+static void
+scherzo_set_key (scherzo_t *scherzo, pitch_t pitch)
+{
+ scherzo_key_init (&scherzo->key, pitch);
+ score_set_key (scherzo->score, pitch);
+}
+
+static bool
+pitches_are_diatonic_scale (pitch_t *pitches, int num_pitches)
+{
+ int diatonic_half_steps[7] = {
+ 0, 2, 4, 5, 7, 9, 11
+ };
+ int half_steps;
+ pitch_t root;
+ int i;
+
+ if (num_pitches < 7)
+ return 0;
+
+ root = pitches[0];
+
+ for (i = 0; i < 7; i++) {
+ half_steps = pitch_from_root_in_half_steps (pitches[i], root);
+ if (half_steps != diatonic_half_steps[i])
+ return false;
+ }
+
+ return true;
+}
+
+static void
+scherzo_press_note (scherzo_t *scherzo, pitch_t pitch)
+{
+ int i;
+
+ pitch = scherzo_key_spell_pitch (&scherzo->key, pitch);
+
+#define NUM_RECENT_PITCHES 7
+ static pitch_t recent_pitches[NUM_RECENT_PITCHES];
+
+ memmove (recent_pitches, recent_pitches + 1,
+ (NUM_RECENT_PITCHES - 1) * sizeof (pitch_t));
+ recent_pitches[NUM_RECENT_PITCHES - 1] = pitch;
+
+ if (pitches_are_diatonic_scale (recent_pitches, NUM_RECENT_PITCHES)) {
+ scherzo_set_key (scherzo, recent_pitches[0]);
+
+ /* Respell pitch according to new key. */
+ pitch = scherzo_key_spell_pitch (&scherzo->key, pitch);
+ }
+
+ /* Do nothing if this note is already pressed. */
+ for (i = 0; i < scherzo->notes_pressed.num_pitches; i++)
+ if (scherzo->notes_pressed.pitches[i] == pitch)
+ return;
+
+ pitch_group_add_pitch (&scherzo->notes_pressed, pitch);
+
+ if (scherzo->pedal_pressed)
+ pitch_group_add_pitch (&scherzo->notes_pedaled, pitch);
+
+ scherzo_update_notes_and_chord (scherzo);
+}
+