Soundtrack expanded to 35 pieces with a leitmotif variant generator and 8 new instruments

- generator: leitmotif as scale degrees, keys/modes, augmentation, diminution, inversion,
  fragment sequences, accompaniment and drum styles; hand-written title 2, boss themes, victory 2
- organ, bell, choir, sub bass, tom, crash, harp, timpani; 8-bit samples, unused instruments stripped
- src/tracks.rs generated with categories; music director with boss themes and room moods
- all pieces validated with libopenmpt; notes checked to stay in key

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/audio.rs

@@ -3,32 +3,30 @@
 // which starts the AudioContext on the first user interaction.
 
 use crate::sfx;
+use crate::tracks::TRACKS;
 use crate::xm::{self, Module, Player};
 use std::cell::RefCell;
 use std::rc::Rc;
 
+// Music categories; the tracks themselves are listed in tracks.rs (generated by the composer)
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub enum Track {
+pub enum Category {
     Title,
-    Build1,
-    Build2,
-    Build3,
-    Battle1,
-    Battle2,
+    Build,
+    Battle,
+    Assault,
+    BossPaladin,
+    BossWarden,
+    Torture,
+    Temple,
     Victory,
     Defeat,
 }
 
-const TRACKS: [(Track, &[u8]); 8] = [
-    (Track::Title, include_bytes!("../assets/music/title.xm")),
-    (Track::Build1, include_bytes!("../assets/music/build1.xm")),
-    (Track::Build2, include_bytes!("../assets/music/build2.xm")),
-    (Track::Build3, include_bytes!("../assets/music/build3.xm")),
-    (Track::Battle1, include_bytes!("../assets/music/battle1.xm")),
-    (Track::Battle2, include_bytes!("../assets/music/battle2.xm")),
-    (Track::Victory, include_bytes!("../assets/music/victory.xm")),
-    (Track::Defeat, include_bytes!("../assets/music/defeat.xm")),
-];
+// indices of all tracks of a category, in play order
+pub fn tracks_in(c: Category) -> Vec<usize> {
+    TRACKS.iter().enumerate().filter(|(_, t)| t.1 == c).map(|(i, _)| i).collect()
+}
 
 const MUSIC_GAIN: f32 = 0.45; // our replayer is ~4x louder than libopenmpt; leaves headroom for effects
 const SFX_GAIN: f32 = 0.55;
@@ -61,7 +59,7 @@ struct State {
     music_vol: f32,
     sfx_vol: f32,
     muted: bool,
-    track: Option<Track>,
+    track: Option<usize>,
     engine: Option<Engine>,
 }
 
@@ -69,24 +67,20 @@ thread_local! {
     static STATE: RefCell<State> = RefCell::new(State { music_vol: 0.6, sfx_vol: 0.7, muted: false, track: None, engine: None });
 }
 
-fn track_index(t: Track) -> usize {
-    TRACKS.iter().position(|(k, _)| *k == t).unwrap_or(0)
-}
-
 impl Engine {
     fn new(rate: f32) -> Engine {
-        let modules = TRACKS.iter().map(|(_, d)| Rc::new(xm::load(d).expect("built-in music"))).collect();
+        let modules = TRACKS.iter().map(|(_, _, d)| Rc::new(xm::load(d).expect("built-in music"))).collect();
         let sfx = sfx::generate_all(rate).into_iter().map(Rc::new).collect();
         Engine { rate, modules, music: Vec::new(), voices: Vec::new(), sfx, buf: Vec::new() }
     }
 
-    fn start_track(&mut self, t: Track, fade: f32) {
+    fn start_track(&mut self, t: usize, fade: f32) {
         let speed = 1.0 / fade.max(0.01);
         for v in self.music.iter_mut() {
             v.target = 0.0;
             v.speed = speed;
         }
-        let player = Player::new(self.modules[track_index(t)].clone(), self.rate);
+        let player = Player::new(self.modules[t.min(self.modules.len() - 1)].clone(), self.rate);
         let instant = self.music.is_empty() || fade <= 0.0;
         self.music.push(MusicVoice { player, gain: if instant { 1.0 } else { 0.0 }, target: 1.0, speed });
     }
@@ -143,7 +137,7 @@ pub fn set_volumes(music: f32, sfx: f32, muted: bool) {
 }
 
 // Switch music with a crossfade (seconds); does nothing if the track already plays
-pub fn play_music(t: Track, fade: f32) {
+pub fn play_music(t: usize, fade: f32) {
     STATE.with(|s| {
         let mut s = s.borrow_mut();
         if s.track == Some(t) {
@@ -164,7 +158,7 @@ pub fn music_loops() -> u32 {
     })
 }
 
-pub fn current_track() -> Option<Track> {
+pub fn current_track() -> Option<usize> {
     STATE.with(|s| s.borrow().track)
 }
 
@@ -225,11 +219,14 @@ mod tests {
     #[test]
     fn engine_crossfade_and_sfx() {
         dc_audio_init(48000.0);
-        play_music(Track::Build1, 0.0);
+        let build = tracks_in(Category::Build);
+        let battle = tracks_in(Category::Battle);
+        assert_eq!(build.len(), 15);
+        play_music(build[0], 0.0);
         let mut peak = 0.0f32;
         for k in 0..200 {
             if k == 50 {
-                play_music(Track::Battle1, 2.5);
+                play_music(battle[0], 2.5);
             }
             if k % 10 == 0 {
                 play_sfx(k % crate::game::SFX_ALL.len(), 1.0, 0.3);
@@ -243,6 +240,6 @@ mod tests {
             }
         }
         assert!(peak > 0.05);
-        assert_eq!(current_track(), Some(Track::Battle1));
+        assert_eq!(current_track(), Some(battle[0]));
     }
 }