third music channel

music.asm

@@ -11,6 +11,12 @@
 ;              is a soft sine, but pulse carries better here)
 ;     voice 2: drums (sfx 61, TIC-80 noise -> SID noise,
 ;              C-1 = kick, C-4 = snare)
+;     voice 3: echo canon: repeats the bass melody 2 rows
+;              (~170 ms) later, 3 octaves up, with the sfx 56
+;              pluck timbre (triangle, decaying envelope);
+;              repeated notes bounce up one more octave. The
+;              echo data lives on the same 128-row grid as the
+;              bass, so the two voices can never drift apart.
 ;   Original timing: tempo 150, speed 5 = 12 rows/s at 60 Hz.
 ;   On PAL (50 Hz) that is 25 frames per 6 rows, so every
 ;   sixth row lasts 5 frames instead of 4 (see spd_tbl).
@@ -53,6 +59,8 @@ BASS_ON   = $41                 ; pulse + gate (much louder than triangle,
 BASS_OFF  = $40                 ;   so the bass stands out from the drums)
 DRUM_ON   = $81                 ; noise + gate
 DRUM_OFF  = $80
+LEAD_ON   = $11                 ; triangle + gate (soft pluck, stays
+LEAD_OFF  = $10                 ;   behind the bass and the drums)
 
 SONG_LEN  = 128                 ; 2 frames x 64 rows
 
@@ -77,6 +85,10 @@ mi_clr:
     sta SID_V2_AD
     lda #$00
     sta SID_V2_SR
+    lda #$06                    ; lead: pluck, ~200 ms decay to zero
+    sta SID_V3_AD               ;   (matches the sfx 56 envelope)
+    lda #$00
+    sta SID_V3_SR
 
     lda #$0f                    ; master volume = 15
     sta SID_VOL
@@ -142,12 +154,12 @@ mp_bass_note:
     ; ---- voice 2: drums ----
 mp_drums:
     lda drum_pat,x
-    beq mp_next
+    beq mp_lead
     cmp #1
     bne mp_drum_note
     lda #DRUM_OFF
     sta SID_V2_CR
-    jmp mp_next
+    jmp mp_lead
 mp_drum_note:
     and #$7f
     tay
@@ -160,6 +172,21 @@ mp_drum_note:
     lda #DRUM_ON
     sta SID_V2_CR
 
+    ; ---- voice 3: arpeggio lead ----
+mp_lead:
+    lda lead_pat,x              ; only notes here, no key-off events:
+    beq mp_next                 ;   the envelope decays to silence
+    and #$7f
+    tay
+    lda lead_flo,y
+    sta SID_V3_FL
+    lda lead_fhi,y
+    sta SID_V3_FH
+    lda #LEAD_OFF
+    sta SID_V3_CR
+    lda #LEAD_ON
+    sta SID_V3_CR
+
 mp_next:
     inx
     cpx #SONG_LEN
@@ -207,6 +234,10 @@ bass_fhi: !byte $04,$03,$05,$05
 ;        0 = C-1 kick (low rumble), 1 = C-4 snare (bright)
 drum_flo: !byte $9c,$ff
 drum_fhi: !byte $45,$ff
+; lead echo: bass notes +3 octaves (0-3), +4 octaves (4-7)
+;   0 = C-5, 1 = A#4, 2 = D#5, 3 = F-5, 4 = C-6, 5 = A#5, 6 = D#6, 7 = F-6
+lead_flo: !byte $ce,$02,$64,$76,$9c,$04,$c8,$eb
+lead_fhi: !byte $22,$1f,$29,$2e,$45,$3e,$52,$5c
 
 ; ---- pattern data: one byte per row per voice ----
 ;   $00 = nothing, $01 = key off, $80|n = play note n
@@ -228,3 +259,14 @@ drum_pat:
     !byte $80,$00,$00,$00,$00,$00,$80,$00,$81,$00,$00,$00,$00,$00,$00,$00
     !byte $80,$00,$00,$00,$00,$00,$00,$00,$81,$00,$00,$00,$00,$00,$00,$00
     !byte $80,$00,$00,$00,$00,$00,$80,$00,$81,$00,$00,$00,$00,$00,$00,$00
+; the bass_pat notes shifted 2 rows later; repeated notes take the
+; octave-up variant (indices 4-7), alternating with the base octave
+lead_pat:
+    !byte $00,$00,$80,$00,$00,$00,$00,$00,$84,$00,$00,$00,$00,$00,$81,$00
+    !byte $80,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
+    !byte $00,$00,$84,$00,$00,$00,$00,$00,$80,$00,$00,$00,$00,$00,$81,$00
+    !byte $80,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
+    !byte $00,$00,$84,$00,$00,$00,$00,$00,$80,$00,$00,$00,$00,$00,$81,$00
+    !byte $80,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
+    !byte $00,$00,$82,$00,$86,$00,$00,$00,$82,$00,$00,$00,$00,$00,$86,$00
+    !byte $83,$00,$00,$00,$87,$00,$00,$00,$83,$00,$87,$00,$00,$00,$83,$00