diff --git a/app/src/main/java/com/lukas/music/instruments/Instrument.kt b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
index 72db3a1..811d16c 100644
--- a/app/src/main/java/com/lukas/music/instruments/Instrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
@@ -1,6 +1,7 @@
 package com.lukas.music.instruments
 
 import com.lukas.music.databinding.FragmentInstrumentBinding
+import com.lukas.music.song.note.Note
 
 abstract class Instrument(private var name: String) {
     private var active = false
@@ -17,7 +18,7 @@
         binding.activeSwitch.isChecked = active
     }
 
-    abstract fun startNote(frequency: Double)
+    abstract fun startNote(note: Note)
     abstract fun changeActive(newActive: Boolean)
 
     companion object {

diff --git a/app/src/main/java/com/lukas/music/instruments/Instrument.kt b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
index 72db3a1..811d16c 100644
--- a/app/src/main/java/com/lukas/music/instruments/Instrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
@@ -1,6 +1,7 @@
 package com.lukas.music.instruments
 
 import com.lukas.music.databinding.FragmentInstrumentBinding
+import com.lukas.music.song.note.Note
 
 abstract class Instrument(private var name: String) {
     private var active = false
@@ -17,7 +18,7 @@
         binding.activeSwitch.isChecked = active
     }
 
-    abstract fun startNote(frequency: Double)
+    abstract fun startNote(note: Note)
     abstract fun changeActive(newActive: Boolean)
 
     companion object {
diff --git a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
index d7460d4..1b53d5d 100644
--- a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
@@ -1,11 +1,12 @@
 package com.lukas.music.instruments
 
+import com.lukas.music.song.note.Note
+
 class MonoInstrument(name: String) : Instrument(name) {
     private val internalInstrument = InternalInstrument()
 
-    override fun startNote(frequency: Double) {
-        println("note $frequency")
-        internalInstrument.startNote(frequency)
+    override fun startNote(note: Note) {
+        internalInstrument.startNote(note.frequency)
     }
 
     override fun changeActive(newActive: Boolean) {

diff --git a/app/src/main/java/com/lukas/music/instruments/Instrument.kt b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
index 72db3a1..811d16c 100644
--- a/app/src/main/java/com/lukas/music/instruments/Instrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
@@ -1,6 +1,7 @@
 package com.lukas.music.instruments
 
 import com.lukas.music.databinding.FragmentInstrumentBinding
+import com.lukas.music.song.note.Note
 
 abstract class Instrument(private var name: String) {
     private var active = false
@@ -17,7 +18,7 @@
         binding.activeSwitch.isChecked = active
     }
 
-    abstract fun startNote(frequency: Double)
+    abstract fun startNote(note: Note)
     abstract fun changeActive(newActive: Boolean)
 
     companion object {
diff --git a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
index d7460d4..1b53d5d 100644
--- a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
@@ -1,11 +1,12 @@
 package com.lukas.music.instruments
 
+import com.lukas.music.song.note.Note
+
 class MonoInstrument(name: String) : Instrument(name) {
     private val internalInstrument = InternalInstrument()
 
-    override fun startNote(frequency: Double) {
-        println("note $frequency")
-        internalInstrument.startNote(frequency)
+    override fun startNote(note: Note) {
+        internalInstrument.startNote(note.frequency)
     }
 
     override fun changeActive(newActive: Boolean) {
diff --git a/app/src/main/java/com/lukas/music/song/Chord.kt b/app/src/main/java/com/lukas/music/song/Chord.kt
index 0b224db..c3328f1 100644
--- a/app/src/main/java/com/lukas/music/song/Chord.kt
+++ b/app/src/main/java/com/lukas/music/song/Chord.kt
@@ -1,3 +1,3 @@
 package com.lukas.music.song
 
-class Chord(val root: Double)
\ No newline at end of file
+class Chord(val note: Int, val chordType: ChordType)
\ No newline at end of file

diff --git a/app/src/main/java/com/lukas/music/instruments/Instrument.kt b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
index 72db3a1..811d16c 100644
--- a/app/src/main/java/com/lukas/music/instruments/Instrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
@@ -1,6 +1,7 @@
 package com.lukas.music.instruments
 
 import com.lukas.music.databinding.FragmentInstrumentBinding
+import com.lukas.music.song.note.Note
 
 abstract class Instrument(private var name: String) {
     private var active = false
@@ -17,7 +18,7 @@
         binding.activeSwitch.isChecked = active
     }
 
-    abstract fun startNote(frequency: Double)
+    abstract fun startNote(note: Note)
     abstract fun changeActive(newActive: Boolean)
 
     companion object {
diff --git a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
index d7460d4..1b53d5d 100644
--- a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
@@ -1,11 +1,12 @@
 package com.lukas.music.instruments
 
+import com.lukas.music.song.note.Note
+
 class MonoInstrument(name: String) : Instrument(name) {
     private val internalInstrument = InternalInstrument()
 
-    override fun startNote(frequency: Double) {
-        println("note $frequency")
-        internalInstrument.startNote(frequency)
+    override fun startNote(note: Note) {
+        internalInstrument.startNote(note.frequency)
     }
 
     override fun changeActive(newActive: Boolean) {
diff --git a/app/src/main/java/com/lukas/music/song/Chord.kt b/app/src/main/java/com/lukas/music/song/Chord.kt
index 0b224db..c3328f1 100644
--- a/app/src/main/java/com/lukas/music/song/Chord.kt
+++ b/app/src/main/java/com/lukas/music/song/Chord.kt
@@ -1,3 +1,3 @@
 package com.lukas.music.song
 
-class Chord(val root: Double)
\ No newline at end of file
+class Chord(val note: Int, val chordType: ChordType)
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/ChordType.kt b/app/src/main/java/com/lukas/music/song/ChordType.kt
new file mode 100644
index 0000000..a68adb6
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/ChordType.kt
@@ -0,0 +1,7 @@
+package com.lukas.music.song
+
+enum class ChordType(private val notes: Array<Int>) {
+    Major(arrayOf(0, 4, 7)),
+    Minor(arrayOf(0, 3, 7)),
+    ;
+}
\ No newline at end of file

diff --git a/app/src/main/java/com/lukas/music/instruments/Instrument.kt b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
index 72db3a1..811d16c 100644
--- a/app/src/main/java/com/lukas/music/instruments/Instrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
@@ -1,6 +1,7 @@
 package com.lukas.music.instruments
 
 import com.lukas.music.databinding.FragmentInstrumentBinding
+import com.lukas.music.song.note.Note
 
 abstract class Instrument(private var name: String) {
     private var active = false
@@ -17,7 +18,7 @@
         binding.activeSwitch.isChecked = active
     }
 
-    abstract fun startNote(frequency: Double)
+    abstract fun startNote(note: Note)
     abstract fun changeActive(newActive: Boolean)
 
     companion object {
diff --git a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
index d7460d4..1b53d5d 100644
--- a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
@@ -1,11 +1,12 @@
 package com.lukas.music.instruments
 
+import com.lukas.music.song.note.Note
+
 class MonoInstrument(name: String) : Instrument(name) {
     private val internalInstrument = InternalInstrument()
 
-    override fun startNote(frequency: Double) {
-        println("note $frequency")
-        internalInstrument.startNote(frequency)
+    override fun startNote(note: Note) {
+        internalInstrument.startNote(note.frequency)
     }
 
     override fun changeActive(newActive: Boolean) {
diff --git a/app/src/main/java/com/lukas/music/song/Chord.kt b/app/src/main/java/com/lukas/music/song/Chord.kt
index 0b224db..c3328f1 100644
--- a/app/src/main/java/com/lukas/music/song/Chord.kt
+++ b/app/src/main/java/com/lukas/music/song/Chord.kt
@@ -1,3 +1,3 @@
 package com.lukas.music.song
 
-class Chord(val root: Double)
\ No newline at end of file
+class Chord(val note: Int, val chordType: ChordType)
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/ChordType.kt b/app/src/main/java/com/lukas/music/song/ChordType.kt
new file mode 100644
index 0000000..a68adb6
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/ChordType.kt
@@ -0,0 +1,7 @@
+package com.lukas.music.song
+
+enum class ChordType(private val notes: Array<Int>) {
+    Major(arrayOf(0, 4, 7)),
+    Minor(arrayOf(0, 3, 7)),
+    ;
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/Note.kt b/app/src/main/java/com/lukas/music/song/Note.kt
deleted file mode 100644
index e81286f..0000000
--- a/app/src/main/java/com/lukas/music/song/Note.kt
+++ /dev/null
@@ -1,3 +0,0 @@
-package com.lukas.music.song
-
-class Note
\ No newline at end of file

diff --git a/app/src/main/java/com/lukas/music/instruments/Instrument.kt b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
index 72db3a1..811d16c 100644
--- a/app/src/main/java/com/lukas/music/instruments/Instrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
@@ -1,6 +1,7 @@
 package com.lukas.music.instruments
 
 import com.lukas.music.databinding.FragmentInstrumentBinding
+import com.lukas.music.song.note.Note
 
 abstract class Instrument(private var name: String) {
     private var active = false
@@ -17,7 +18,7 @@
         binding.activeSwitch.isChecked = active
     }
 
-    abstract fun startNote(frequency: Double)
+    abstract fun startNote(note: Note)
     abstract fun changeActive(newActive: Boolean)
 
     companion object {
diff --git a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
index d7460d4..1b53d5d 100644
--- a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
@@ -1,11 +1,12 @@
 package com.lukas.music.instruments
 
+import com.lukas.music.song.note.Note
+
 class MonoInstrument(name: String) : Instrument(name) {
     private val internalInstrument = InternalInstrument()
 
-    override fun startNote(frequency: Double) {
-        println("note $frequency")
-        internalInstrument.startNote(frequency)
+    override fun startNote(note: Note) {
+        internalInstrument.startNote(note.frequency)
     }
 
     override fun changeActive(newActive: Boolean) {
diff --git a/app/src/main/java/com/lukas/music/song/Chord.kt b/app/src/main/java/com/lukas/music/song/Chord.kt
index 0b224db..c3328f1 100644
--- a/app/src/main/java/com/lukas/music/song/Chord.kt
+++ b/app/src/main/java/com/lukas/music/song/Chord.kt
@@ -1,3 +1,3 @@
 package com.lukas.music.song
 
-class Chord(val root: Double)
\ No newline at end of file
+class Chord(val note: Int, val chordType: ChordType)
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/ChordType.kt b/app/src/main/java/com/lukas/music/song/ChordType.kt
new file mode 100644
index 0000000..a68adb6
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/ChordType.kt
@@ -0,0 +1,7 @@
+package com.lukas.music.song
+
+enum class ChordType(private val notes: Array<Int>) {
+    Major(arrayOf(0, 4, 7)),
+    Minor(arrayOf(0, 3, 7)),
+    ;
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/Note.kt b/app/src/main/java/com/lukas/music/song/Note.kt
deleted file mode 100644
index e81286f..0000000
--- a/app/src/main/java/com/lukas/music/song/Note.kt
+++ /dev/null
@@ -1,3 +0,0 @@
-package com.lukas.music.song
-
-class Note
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/Song.kt b/app/src/main/java/com/lukas/music/song/Song.kt
index a7c440a..9f9dd78 100644
--- a/app/src/main/java/com/lukas/music/song/Song.kt
+++ b/app/src/main/java/com/lukas/music/song/Song.kt
@@ -1,24 +1,35 @@
 package com.lukas.music.song
 
 import com.lukas.music.instruments.Instrument
+import com.lukas.music.song.note.Note
+import com.lukas.music.song.note.NoteName
 
 class Song(
-    private val chordProgression: ChordProgression
+    private val root: Note,
+    private val chordProgression: ChordProgression,
 ) {
     fun step() {
         val chord = chordProgression.step()
         for (instrument in Instrument.instruments) {
-            instrument.startNote(chord.root)
+            instrument.startNote(root + chord.note)
         }
     }
 
     companion object {
         var currentSong = Song(
+            Note.of(NoteName.F, 4),
             ChordProgression(
                 listOf(
-                    Chord(130.82), Chord(164.82), Chord(174.62)
+                    Chord(1, ChordType.Major),
+                    Chord(6, ChordType.Major),
+                    Chord(2, ChordType.Minor),
+                    Chord(8, ChordType.Major),
                 )
             )
         )
+
+        init {
+            println("root:  ${currentSong.root.frequency}")
+        }
     }
 }
\ No newline at end of file

diff --git a/app/src/main/java/com/lukas/music/instruments/Instrument.kt b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
index 72db3a1..811d16c 100644
--- a/app/src/main/java/com/lukas/music/instruments/Instrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
@@ -1,6 +1,7 @@
 package com.lukas.music.instruments
 
 import com.lukas.music.databinding.FragmentInstrumentBinding
+import com.lukas.music.song.note.Note
 
 abstract class Instrument(private var name: String) {
     private var active = false
@@ -17,7 +18,7 @@
         binding.activeSwitch.isChecked = active
     }
 
-    abstract fun startNote(frequency: Double)
+    abstract fun startNote(note: Note)
     abstract fun changeActive(newActive: Boolean)
 
     companion object {
diff --git a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
index d7460d4..1b53d5d 100644
--- a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
@@ -1,11 +1,12 @@
 package com.lukas.music.instruments
 
+import com.lukas.music.song.note.Note
+
 class MonoInstrument(name: String) : Instrument(name) {
     private val internalInstrument = InternalInstrument()
 
-    override fun startNote(frequency: Double) {
-        println("note $frequency")
-        internalInstrument.startNote(frequency)
+    override fun startNote(note: Note) {
+        internalInstrument.startNote(note.frequency)
     }
 
     override fun changeActive(newActive: Boolean) {
diff --git a/app/src/main/java/com/lukas/music/song/Chord.kt b/app/src/main/java/com/lukas/music/song/Chord.kt
index 0b224db..c3328f1 100644
--- a/app/src/main/java/com/lukas/music/song/Chord.kt
+++ b/app/src/main/java/com/lukas/music/song/Chord.kt
@@ -1,3 +1,3 @@
 package com.lukas.music.song
 
-class Chord(val root: Double)
\ No newline at end of file
+class Chord(val note: Int, val chordType: ChordType)
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/ChordType.kt b/app/src/main/java/com/lukas/music/song/ChordType.kt
new file mode 100644
index 0000000..a68adb6
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/ChordType.kt
@@ -0,0 +1,7 @@
+package com.lukas.music.song
+
+enum class ChordType(private val notes: Array<Int>) {
+    Major(arrayOf(0, 4, 7)),
+    Minor(arrayOf(0, 3, 7)),
+    ;
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/Note.kt b/app/src/main/java/com/lukas/music/song/Note.kt
deleted file mode 100644
index e81286f..0000000
--- a/app/src/main/java/com/lukas/music/song/Note.kt
+++ /dev/null
@@ -1,3 +0,0 @@
-package com.lukas.music.song
-
-class Note
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/Song.kt b/app/src/main/java/com/lukas/music/song/Song.kt
index a7c440a..9f9dd78 100644
--- a/app/src/main/java/com/lukas/music/song/Song.kt
+++ b/app/src/main/java/com/lukas/music/song/Song.kt
@@ -1,24 +1,35 @@
 package com.lukas.music.song
 
 import com.lukas.music.instruments.Instrument
+import com.lukas.music.song.note.Note
+import com.lukas.music.song.note.NoteName
 
 class Song(
-    private val chordProgression: ChordProgression
+    private val root: Note,
+    private val chordProgression: ChordProgression,
 ) {
     fun step() {
         val chord = chordProgression.step()
         for (instrument in Instrument.instruments) {
-            instrument.startNote(chord.root)
+            instrument.startNote(root + chord.note)
         }
     }
 
     companion object {
         var currentSong = Song(
+            Note.of(NoteName.F, 4),
             ChordProgression(
                 listOf(
-                    Chord(130.82), Chord(164.82), Chord(174.62)
+                    Chord(1, ChordType.Major),
+                    Chord(6, ChordType.Major),
+                    Chord(2, ChordType.Minor),
+                    Chord(8, ChordType.Major),
                 )
             )
         )
+
+        init {
+            println("root:  ${currentSong.root.frequency}")
+        }
     }
 }
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/note/Note.kt b/app/src/main/java/com/lukas/music/song/note/Note.kt
new file mode 100644
index 0000000..0005d13
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/note/Note.kt
@@ -0,0 +1,28 @@
+package com.lukas.music.song.note
+
+import kotlin.math.pow
+
+class Note(val id: Int) {
+    val noteName = NoteName.VALUES[id % NoteName.VALUES.size]
+    val octave = id / NoteName.VALUES.size - 1
+    val frequency = noteName.baseFrequency * 2.0.pow(id / NoteName.VALUES.size - 5)
+
+    operator fun plus(other: Int): Note {
+        if (other < 0 || other > 127) {
+            throw IllegalArgumentException("cannot add $other to note with id $id")
+        }
+        return NOTES[id + other]
+    }
+
+    operator fun minus(other: Int): Note {
+        return this + (-other)
+    }
+
+    companion object {
+        val NOTES = Array(128) { Note(it) }
+
+        fun of(noteName: NoteName, octave: Int): Note {
+            return NOTES[NoteName.VALUES.size * (octave + 1) + noteName.index]
+        }
+    }
+}
\ No newline at end of file

diff --git a/app/src/main/java/com/lukas/music/instruments/Instrument.kt b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
index 72db3a1..811d16c 100644
--- a/app/src/main/java/com/lukas/music/instruments/Instrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
@@ -1,6 +1,7 @@
 package com.lukas.music.instruments
 
 import com.lukas.music.databinding.FragmentInstrumentBinding
+import com.lukas.music.song.note.Note
 
 abstract class Instrument(private var name: String) {
     private var active = false
@@ -17,7 +18,7 @@
         binding.activeSwitch.isChecked = active
     }
 
-    abstract fun startNote(frequency: Double)
+    abstract fun startNote(note: Note)
     abstract fun changeActive(newActive: Boolean)
 
     companion object {
diff --git a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
index d7460d4..1b53d5d 100644
--- a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
@@ -1,11 +1,12 @@
 package com.lukas.music.instruments
 
+import com.lukas.music.song.note.Note
+
 class MonoInstrument(name: String) : Instrument(name) {
     private val internalInstrument = InternalInstrument()
 
-    override fun startNote(frequency: Double) {
-        println("note $frequency")
-        internalInstrument.startNote(frequency)
+    override fun startNote(note: Note) {
+        internalInstrument.startNote(note.frequency)
     }
 
     override fun changeActive(newActive: Boolean) {
diff --git a/app/src/main/java/com/lukas/music/song/Chord.kt b/app/src/main/java/com/lukas/music/song/Chord.kt
index 0b224db..c3328f1 100644
--- a/app/src/main/java/com/lukas/music/song/Chord.kt
+++ b/app/src/main/java/com/lukas/music/song/Chord.kt
@@ -1,3 +1,3 @@
 package com.lukas.music.song
 
-class Chord(val root: Double)
\ No newline at end of file
+class Chord(val note: Int, val chordType: ChordType)
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/ChordType.kt b/app/src/main/java/com/lukas/music/song/ChordType.kt
new file mode 100644
index 0000000..a68adb6
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/ChordType.kt
@@ -0,0 +1,7 @@
+package com.lukas.music.song
+
+enum class ChordType(private val notes: Array<Int>) {
+    Major(arrayOf(0, 4, 7)),
+    Minor(arrayOf(0, 3, 7)),
+    ;
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/Note.kt b/app/src/main/java/com/lukas/music/song/Note.kt
deleted file mode 100644
index e81286f..0000000
--- a/app/src/main/java/com/lukas/music/song/Note.kt
+++ /dev/null
@@ -1,3 +0,0 @@
-package com.lukas.music.song
-
-class Note
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/Song.kt b/app/src/main/java/com/lukas/music/song/Song.kt
index a7c440a..9f9dd78 100644
--- a/app/src/main/java/com/lukas/music/song/Song.kt
+++ b/app/src/main/java/com/lukas/music/song/Song.kt
@@ -1,24 +1,35 @@
 package com.lukas.music.song
 
 import com.lukas.music.instruments.Instrument
+import com.lukas.music.song.note.Note
+import com.lukas.music.song.note.NoteName
 
 class Song(
-    private val chordProgression: ChordProgression
+    private val root: Note,
+    private val chordProgression: ChordProgression,
 ) {
     fun step() {
         val chord = chordProgression.step()
         for (instrument in Instrument.instruments) {
-            instrument.startNote(chord.root)
+            instrument.startNote(root + chord.note)
         }
     }
 
     companion object {
         var currentSong = Song(
+            Note.of(NoteName.F, 4),
             ChordProgression(
                 listOf(
-                    Chord(130.82), Chord(164.82), Chord(174.62)
+                    Chord(1, ChordType.Major),
+                    Chord(6, ChordType.Major),
+                    Chord(2, ChordType.Minor),
+                    Chord(8, ChordType.Major),
                 )
             )
         )
+
+        init {
+            println("root:  ${currentSong.root.frequency}")
+        }
     }
 }
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/note/Note.kt b/app/src/main/java/com/lukas/music/song/note/Note.kt
new file mode 100644
index 0000000..0005d13
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/note/Note.kt
@@ -0,0 +1,28 @@
+package com.lukas.music.song.note
+
+import kotlin.math.pow
+
+class Note(val id: Int) {
+    val noteName = NoteName.VALUES[id % NoteName.VALUES.size]
+    val octave = id / NoteName.VALUES.size - 1
+    val frequency = noteName.baseFrequency * 2.0.pow(id / NoteName.VALUES.size - 5)
+
+    operator fun plus(other: Int): Note {
+        if (other < 0 || other > 127) {
+            throw IllegalArgumentException("cannot add $other to note with id $id")
+        }
+        return NOTES[id + other]
+    }
+
+    operator fun minus(other: Int): Note {
+        return this + (-other)
+    }
+
+    companion object {
+        val NOTES = Array(128) { Note(it) }
+
+        fun of(noteName: NoteName, octave: Int): Note {
+            return NOTES[NoteName.VALUES.size * (octave + 1) + noteName.index]
+        }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/note/NoteName.kt b/app/src/main/java/com/lukas/music/song/note/NoteName.kt
new file mode 100644
index 0000000..49c19b2
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/note/NoteName.kt
@@ -0,0 +1,32 @@
+package com.lukas.music.song.note
+
+import kotlin.math.pow
+
+const val A4 = 440.0
+
+enum class NoteName(val index: Int, val asString: String) {
+    C(0, "C"),
+    Csharp(1, "C#"),
+    D(2, "D"),
+    Dsharp(3, "D#"),
+    E(4, "E"),
+    F(5, "F"),
+    Fsharp(6, "F#"),
+    G(7, "G"),
+    Gsharp(8, "G#"),
+    A(9, "A"),
+    Asharp(10, "A#"),
+    B(11, "B"),
+    ;
+
+    val baseFrequency: Double = A4 * 2.0.pow(index.toDouble() / 12)
+
+    operator fun plus(interval: Int): NoteName {
+        val resultPosition = (index + interval) % VALUES.size
+        return VALUES[resultPosition]
+    }
+
+    companion object {
+        val VALUES = values()
+    }
+}
\ No newline at end of file

diff --git a/app/src/main/java/com/lukas/music/instruments/Instrument.kt b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
index 72db3a1..811d16c 100644
--- a/app/src/main/java/com/lukas/music/instruments/Instrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
@@ -1,6 +1,7 @@
 package com.lukas.music.instruments
 
 import com.lukas.music.databinding.FragmentInstrumentBinding
+import com.lukas.music.song.note.Note
 
 abstract class Instrument(private var name: String) {
     private var active = false
@@ -17,7 +18,7 @@
         binding.activeSwitch.isChecked = active
     }
 
-    abstract fun startNote(frequency: Double)
+    abstract fun startNote(note: Note)
     abstract fun changeActive(newActive: Boolean)
 
     companion object {
diff --git a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
index d7460d4..1b53d5d 100644
--- a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
@@ -1,11 +1,12 @@
 package com.lukas.music.instruments
 
+import com.lukas.music.song.note.Note
+
 class MonoInstrument(name: String) : Instrument(name) {
     private val internalInstrument = InternalInstrument()
 
-    override fun startNote(frequency: Double) {
-        println("note $frequency")
-        internalInstrument.startNote(frequency)
+    override fun startNote(note: Note) {
+        internalInstrument.startNote(note.frequency)
     }
 
     override fun changeActive(newActive: Boolean) {
diff --git a/app/src/main/java/com/lukas/music/song/Chord.kt b/app/src/main/java/com/lukas/music/song/Chord.kt
index 0b224db..c3328f1 100644
--- a/app/src/main/java/com/lukas/music/song/Chord.kt
+++ b/app/src/main/java/com/lukas/music/song/Chord.kt
@@ -1,3 +1,3 @@
 package com.lukas.music.song
 
-class Chord(val root: Double)
\ No newline at end of file
+class Chord(val note: Int, val chordType: ChordType)
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/ChordType.kt b/app/src/main/java/com/lukas/music/song/ChordType.kt
new file mode 100644
index 0000000..a68adb6
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/ChordType.kt
@@ -0,0 +1,7 @@
+package com.lukas.music.song
+
+enum class ChordType(private val notes: Array<Int>) {
+    Major(arrayOf(0, 4, 7)),
+    Minor(arrayOf(0, 3, 7)),
+    ;
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/Note.kt b/app/src/main/java/com/lukas/music/song/Note.kt
deleted file mode 100644
index e81286f..0000000
--- a/app/src/main/java/com/lukas/music/song/Note.kt
+++ /dev/null
@@ -1,3 +0,0 @@
-package com.lukas.music.song
-
-class Note
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/Song.kt b/app/src/main/java/com/lukas/music/song/Song.kt
index a7c440a..9f9dd78 100644
--- a/app/src/main/java/com/lukas/music/song/Song.kt
+++ b/app/src/main/java/com/lukas/music/song/Song.kt
@@ -1,24 +1,35 @@
 package com.lukas.music.song
 
 import com.lukas.music.instruments.Instrument
+import com.lukas.music.song.note.Note
+import com.lukas.music.song.note.NoteName
 
 class Song(
-    private val chordProgression: ChordProgression
+    private val root: Note,
+    private val chordProgression: ChordProgression,
 ) {
     fun step() {
         val chord = chordProgression.step()
         for (instrument in Instrument.instruments) {
-            instrument.startNote(chord.root)
+            instrument.startNote(root + chord.note)
         }
     }
 
     companion object {
         var currentSong = Song(
+            Note.of(NoteName.F, 4),
             ChordProgression(
                 listOf(
-                    Chord(130.82), Chord(164.82), Chord(174.62)
+                    Chord(1, ChordType.Major),
+                    Chord(6, ChordType.Major),
+                    Chord(2, ChordType.Minor),
+                    Chord(8, ChordType.Major),
                 )
             )
         )
+
+        init {
+            println("root:  ${currentSong.root.frequency}")
+        }
     }
 }
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/note/Note.kt b/app/src/main/java/com/lukas/music/song/note/Note.kt
new file mode 100644
index 0000000..0005d13
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/note/Note.kt
@@ -0,0 +1,28 @@
+package com.lukas.music.song.note
+
+import kotlin.math.pow
+
+class Note(val id: Int) {
+    val noteName = NoteName.VALUES[id % NoteName.VALUES.size]
+    val octave = id / NoteName.VALUES.size - 1
+    val frequency = noteName.baseFrequency * 2.0.pow(id / NoteName.VALUES.size - 5)
+
+    operator fun plus(other: Int): Note {
+        if (other < 0 || other > 127) {
+            throw IllegalArgumentException("cannot add $other to note with id $id")
+        }
+        return NOTES[id + other]
+    }
+
+    operator fun minus(other: Int): Note {
+        return this + (-other)
+    }
+
+    companion object {
+        val NOTES = Array(128) { Note(it) }
+
+        fun of(noteName: NoteName, octave: Int): Note {
+            return NOTES[NoteName.VALUES.size * (octave + 1) + noteName.index]
+        }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/note/NoteName.kt b/app/src/main/java/com/lukas/music/song/note/NoteName.kt
new file mode 100644
index 0000000..49c19b2
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/note/NoteName.kt
@@ -0,0 +1,32 @@
+package com.lukas.music.song.note
+
+import kotlin.math.pow
+
+const val A4 = 440.0
+
+enum class NoteName(val index: Int, val asString: String) {
+    C(0, "C"),
+    Csharp(1, "C#"),
+    D(2, "D"),
+    Dsharp(3, "D#"),
+    E(4, "E"),
+    F(5, "F"),
+    Fsharp(6, "F#"),
+    G(7, "G"),
+    Gsharp(8, "G#"),
+    A(9, "A"),
+    Asharp(10, "A#"),
+    B(11, "B"),
+    ;
+
+    val baseFrequency: Double = A4 * 2.0.pow(index.toDouble() / 12)
+
+    operator fun plus(interval: Int): NoteName {
+        val resultPosition = (index + interval) % VALUES.size
+        return VALUES[resultPosition]
+    }
+
+    companion object {
+        val VALUES = values()
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/voice/BassVoice.kt b/app/src/main/java/com/lukas/music/song/voice/BassVoice.kt
new file mode 100644
index 0000000..8714423
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/voice/BassVoice.kt
@@ -0,0 +1,3 @@
+package com.lukas.music.song.voice
+
+class BassVoice
\ No newline at end of file

diff --git a/app/src/main/java/com/lukas/music/instruments/Instrument.kt b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
index 72db3a1..811d16c 100644
--- a/app/src/main/java/com/lukas/music/instruments/Instrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/Instrument.kt
@@ -1,6 +1,7 @@
 package com.lukas.music.instruments
 
 import com.lukas.music.databinding.FragmentInstrumentBinding
+import com.lukas.music.song.note.Note
 
 abstract class Instrument(private var name: String) {
     private var active = false
@@ -17,7 +18,7 @@
         binding.activeSwitch.isChecked = active
     }
 
-    abstract fun startNote(frequency: Double)
+    abstract fun startNote(note: Note)
     abstract fun changeActive(newActive: Boolean)
 
     companion object {
diff --git a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
index d7460d4..1b53d5d 100644
--- a/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
+++ b/app/src/main/java/com/lukas/music/instruments/MonoInstrument.kt
@@ -1,11 +1,12 @@
 package com.lukas.music.instruments
 
+import com.lukas.music.song.note.Note
+
 class MonoInstrument(name: String) : Instrument(name) {
     private val internalInstrument = InternalInstrument()
 
-    override fun startNote(frequency: Double) {
-        println("note $frequency")
-        internalInstrument.startNote(frequency)
+    override fun startNote(note: Note) {
+        internalInstrument.startNote(note.frequency)
     }
 
     override fun changeActive(newActive: Boolean) {
diff --git a/app/src/main/java/com/lukas/music/song/Chord.kt b/app/src/main/java/com/lukas/music/song/Chord.kt
index 0b224db..c3328f1 100644
--- a/app/src/main/java/com/lukas/music/song/Chord.kt
+++ b/app/src/main/java/com/lukas/music/song/Chord.kt
@@ -1,3 +1,3 @@
 package com.lukas.music.song
 
-class Chord(val root: Double)
\ No newline at end of file
+class Chord(val note: Int, val chordType: ChordType)
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/ChordType.kt b/app/src/main/java/com/lukas/music/song/ChordType.kt
new file mode 100644
index 0000000..a68adb6
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/ChordType.kt
@@ -0,0 +1,7 @@
+package com.lukas.music.song
+
+enum class ChordType(private val notes: Array<Int>) {
+    Major(arrayOf(0, 4, 7)),
+    Minor(arrayOf(0, 3, 7)),
+    ;
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/Note.kt b/app/src/main/java/com/lukas/music/song/Note.kt
deleted file mode 100644
index e81286f..0000000
--- a/app/src/main/java/com/lukas/music/song/Note.kt
+++ /dev/null
@@ -1,3 +0,0 @@
-package com.lukas.music.song
-
-class Note
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/Song.kt b/app/src/main/java/com/lukas/music/song/Song.kt
index a7c440a..9f9dd78 100644
--- a/app/src/main/java/com/lukas/music/song/Song.kt
+++ b/app/src/main/java/com/lukas/music/song/Song.kt
@@ -1,24 +1,35 @@
 package com.lukas.music.song
 
 import com.lukas.music.instruments.Instrument
+import com.lukas.music.song.note.Note
+import com.lukas.music.song.note.NoteName
 
 class Song(
-    private val chordProgression: ChordProgression
+    private val root: Note,
+    private val chordProgression: ChordProgression,
 ) {
     fun step() {
         val chord = chordProgression.step()
         for (instrument in Instrument.instruments) {
-            instrument.startNote(chord.root)
+            instrument.startNote(root + chord.note)
         }
     }
 
     companion object {
         var currentSong = Song(
+            Note.of(NoteName.F, 4),
             ChordProgression(
                 listOf(
-                    Chord(130.82), Chord(164.82), Chord(174.62)
+                    Chord(1, ChordType.Major),
+                    Chord(6, ChordType.Major),
+                    Chord(2, ChordType.Minor),
+                    Chord(8, ChordType.Major),
                 )
             )
         )
+
+        init {
+            println("root:  ${currentSong.root.frequency}")
+        }
     }
 }
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/note/Note.kt b/app/src/main/java/com/lukas/music/song/note/Note.kt
new file mode 100644
index 0000000..0005d13
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/note/Note.kt
@@ -0,0 +1,28 @@
+package com.lukas.music.song.note
+
+import kotlin.math.pow
+
+class Note(val id: Int) {
+    val noteName = NoteName.VALUES[id % NoteName.VALUES.size]
+    val octave = id / NoteName.VALUES.size - 1
+    val frequency = noteName.baseFrequency * 2.0.pow(id / NoteName.VALUES.size - 5)
+
+    operator fun plus(other: Int): Note {
+        if (other < 0 || other > 127) {
+            throw IllegalArgumentException("cannot add $other to note with id $id")
+        }
+        return NOTES[id + other]
+    }
+
+    operator fun minus(other: Int): Note {
+        return this + (-other)
+    }
+
+    companion object {
+        val NOTES = Array(128) { Note(it) }
+
+        fun of(noteName: NoteName, octave: Int): Note {
+            return NOTES[NoteName.VALUES.size * (octave + 1) + noteName.index]
+        }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/note/NoteName.kt b/app/src/main/java/com/lukas/music/song/note/NoteName.kt
new file mode 100644
index 0000000..49c19b2
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/note/NoteName.kt
@@ -0,0 +1,32 @@
+package com.lukas.music.song.note
+
+import kotlin.math.pow
+
+const val A4 = 440.0
+
+enum class NoteName(val index: Int, val asString: String) {
+    C(0, "C"),
+    Csharp(1, "C#"),
+    D(2, "D"),
+    Dsharp(3, "D#"),
+    E(4, "E"),
+    F(5, "F"),
+    Fsharp(6, "F#"),
+    G(7, "G"),
+    Gsharp(8, "G#"),
+    A(9, "A"),
+    Asharp(10, "A#"),
+    B(11, "B"),
+    ;
+
+    val baseFrequency: Double = A4 * 2.0.pow(index.toDouble() / 12)
+
+    operator fun plus(interval: Int): NoteName {
+        val resultPosition = (index + interval) % VALUES.size
+        return VALUES[resultPosition]
+    }
+
+    companion object {
+        val VALUES = values()
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/voice/BassVoice.kt b/app/src/main/java/com/lukas/music/song/voice/BassVoice.kt
new file mode 100644
index 0000000..8714423
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/voice/BassVoice.kt
@@ -0,0 +1,3 @@
+package com.lukas.music.song.voice
+
+class BassVoice
\ No newline at end of file
diff --git a/app/src/main/java/com/lukas/music/song/voice/Voice.kt b/app/src/main/java/com/lukas/music/song/voice/Voice.kt
new file mode 100644
index 0000000..df4c83c
--- /dev/null
+++ b/app/src/main/java/com/lukas/music/song/voice/Voice.kt
@@ -0,0 +1,3 @@
+package com.lukas.music.song.voice
+
+class Voice
\ No newline at end of file