✨ StemAtInstant#playcount

src/synchronization/audio.rs

···
     pub duration: usize,
     pub velocity_max: u8,
     pub notes: Vec<Note>,
+    /// How many instants (individual ms values)
+    /// have occurred where this stem played notes
+    /// before this instant (not counting the current instant)
+    pub playcount: usize,
 }
 impl StemAtInstant {
     pub fn amplitude_relative(&self) -> f32 {

src/video/context.rs

···
                 .unwrap_or(0),
             duration: stems[name].duration_ms,
             notes: stems[name].notes.get(&self.ms).cloned().unwrap_or(vec![]),
+            playcount: stems[name]
+                .notes
+                .iter()
+                .filter(|&(&ms, notes)| {
+                    ms < self.ms
+                        && !notes.is_empty()
+                        && notes.iter().any(|note| note.is_on())
+                })
+                .count(),
         }
     }