diff --git a/src/music/mod.rs b/src/music/mod.rs
index 292fdcf..3288ca8 100644
--- a/src/music/mod.rs
+++ b/src/music/mod.rs
@@ -40,9 +40,27 @@ impl<P> Primitive<P> {
 pub type PlayerName = String;
 
 #[derive(Debug, PartialEq, Eq, Copy, Clone, PartialOrd, Ord)]
-pub enum Mode {
-    Major,
-    Minor,
+pub enum KeySig {
+    Major(PitchClass),
+    Minor(PitchClass),
+}
+
+impl Default for KeySig {
+    fn default() -> Self {
+        // the white piano keys
+        Self::Major(PitchClass::C)
+    }
+}
+
+impl KeySig {
+    pub fn get_scale(self) -> impl Iterator<Item = PitchClass> {
+        let oc4 = Octave::ONE_LINED;
+        let with_octave: Box<dyn Iterator<Item = Pitch>> = match self {
+            KeySig::Major(pc) => Box::new(Pitch::new(pc, oc4).major_scale()),
+            KeySig::Minor(pc) => Box::new(Pitch::new(pc, oc4).natural_minor_scale()),
+        };
+        with_octave.map(Pitch::class)
+    }
 }
 
 #[derive(Debug, PartialEq, Eq, Clone, PartialOrd, Ord)]
@@ -52,7 +70,7 @@ pub enum Control {
     Instrument(InstrumentName),
     Phrase(Vec<PhraseAttribute>),
     Player(PlayerName),
-    KeySig(PitchClass, Mode), // key signature and mode
+    KeySig(KeySig),
 }
 
 #[derive(Debug, PartialEq, Eq, Clone, PartialOrd, Ord)]
@@ -147,8 +165,8 @@ impl<P> Music<P> {
         self.with(Control::Player(name))
     }
 
-    pub fn with_key_sig(self, pitch_class: PitchClass, mode: Mode) -> Self {
-        self.with(Control::KeySig(pitch_class, mode))
+    pub fn with_key_sig(self, key_signature: KeySig) -> Self {
+        self.with(Control::KeySig(key_signature))
     }
 
     pub fn duration(&self) -> Dur {
@@ -375,4 +393,40 @@ mod tests {
         let pitch = Pitch::C(Octave(-4));
         assert_is_close_freq(pitch.get_frequency(), 1.022);
     }
+
+    #[test]
+    fn key_sig_c_major_scale() {
+        let scale: Vec<_> = KeySig::Major(PitchClass::C).get_scale().collect();
+        assert_eq!(
+            scale,
+            [
+                PitchClass::C,
+                PitchClass::D,
+                PitchClass::E,
+                PitchClass::F,
+                PitchClass::G,
+                PitchClass::A,
+                PitchClass::B,
+                PitchClass::C,
+            ]
+        );
+    }
+
+    #[test]
+    fn key_sig_g_major_scale() {
+        let scale: Vec<_> = KeySig::Major(PitchClass::G).get_scale().collect();
+        assert_eq!(
+            scale,
+            [
+                PitchClass::G,
+                PitchClass::A,
+                PitchClass::B,
+                PitchClass::C,
+                PitchClass::D,
+                PitchClass::E,
+                PitchClass::Fs,
+                PitchClass::G,
+            ]
+        );
+    }
 }
diff --git a/src/music/performance.rs b/src/music/performance.rs
index 3eb9d15..3de4832 100644
--- a/src/music/performance.rs
+++ b/src/music/performance.rs
@@ -7,8 +7,8 @@ use ordered_float::OrderedFloat;
 use crate::instruments::InstrumentName;
 
 use super::{
-    duration::Dur, interval::AbsPitch, phrases::PhraseAttribute, pitch::PitchClass, Control, Mode,
-    Music, PlayerName, Primitive, Volume,
+    duration::Dur, interval::AbsPitch, phrases::PhraseAttribute, Control, KeySig, Music,
+    PlayerName, Primitive, Volume,
 };
 
 #[derive(Debug)]
@@ -84,8 +84,8 @@ where
                 ctx.player = player;
                 m.perf(players, ctx)
             }
-            Self::Modify(Control::KeySig(pc, mode), m) => {
-                ctx.key = (*pc, *mode);
+            Self::Modify(Control::KeySig(ks), m) => {
+                ctx.key = *ks;
                 m.perf(players, ctx)
             }
         }
@@ -126,7 +126,7 @@ pub struct Context<'p, P> {
     whole_note: Duration,
     pitch: AbsPitch,
     volume: Volume,
-    key: (PitchClass, Mode),
+    key: KeySig,
 }
 
 impl<'p, P> Clone for Context<'p, P> {
@@ -495,7 +495,7 @@ mod defaults {
                 whole_note: metro(120, Dur::QN),
                 pitch: AbsPitch::from(0),
                 volume: Volume::loudest(),
-                key: (PitchClass::C, Mode::Major),
+                key: KeySig::default(),
             }
         }
     }