ldy #&ff
        sty &fe43
        sta &fe4f
        iny
        sty &fe40
        ldy #2
.sndwait dey
        bne sndwait
        ldy #8
        sty &fe40
        rts

setuptimer sei

   lda #$7f  ;Disable all VIA ints
   sta $fe4e
   sta $fe6e

   lda #$c0  ;Enable timer 1
   sta $fe4e

   lda $fe4b
   ora #$40  ;Set bit 6 for free running timer 1
   sta $fe4b

   lda #150  ;1000000/152=6578hz
   sta $fe44 ;change these lines to change frequency!
   lda #0
   sta $fe45

   lda $204        ;set our IRQ handler
   sta OLDIRQ1V
   lda $205
   sta OLDIRQ1V+1
   lda #<irq1v
   sta $204
   lda #>irq1v
   sta $205

   cli

   rts

irq1v   tya
   pha
           txa
           pha

   lda #$40 ;Clear interrupt
   sta $fe4d

           lda SAMPLE ;(insert your own code here to load 4-bit sample)
           ora #VOLCONST ;(&90,&B0,&D0, or &F0 depending on what channel)
           jsr soundwrite

           pla
           tax
           pla
   tay
   lda $FC
   rti

$00001C00: sei
$00001C01: lda #$FF   ;set VIA DDR to output
$00001C03: sta $FE43
$00001C06: lda #$84   ;set all voices to max frequency
$00001C08: jsr $1C65
$00001C0B: lda #$00
$00001C0D: jsr $1C65
$00001C10: lda #$A4
$00001C12: jsr $1C65
$00001C15: lda #$00
$00001C17: jsr $1C65
$00001C1A: lda #$C4
$00001C1C: jsr $1C65
$00001C1F: lda #$00
$00001C21: jsr $1C65
$00001C24: lda #$00
$00001C26: sta $70
$00001C28: lda $75     ;set to $1D by loader, ie sample start $1D00
$00001C2A: sta $71
$00001C2C: ldy #$00
$00001C2E: lda ($70),y
$00001C30: and #$0F
$00001C32: jsr $1C79
$00001C35: ldy #$04
$00001C37: dey
$00001C38: bne $1C37
$00001C3A: lda ($70),y
$00001C3C: and #$F0
$00001C3E: lsr a
$00001C3F: lsr a
$00001C40: lsr a
$00001C41: lsr a
$00001C42: jsr $1C79
$00001C45: inc $70
$00001C47: bne $1C2C
$00001C49: inc $71
$00001C4B: lda $71
$00001C4D: cmp $76     ;set to $76, ie sample end at $75FF
$00001C4F: beq $1C00
$00001C51: lda #$81    ;check if key is pressed
$00001C53: ldx #$9D    ;this actually causes a delay
$00001C55: ldy #$80    ;resulting in a minor bump every 256 samples
$00001C57: jsr $FFF4
$00001C5A: cpx #$FF
$00001C5C: bne $1C2C
$00001C5E: lda #$0F    ;set all voices to no volume - not strictly necessary
$00001C60: jsr $1C79
$00001C63: cli
$00001C64: rts
$00001C65: sta $FE4F   ;write data to soundchip
$00001C68: ldy #$00
$00001C6A: sty $FE40
$00001C6D: nop         ;in a proper player, you'd do something useful with this time
$00001C6E: nop         ;instead of just nop-ing
$00001C6F: nop
$00001C70: nop
$00001C71: nop
$00001C72: nop
$00001C73: ldy #$08
$00001C75: sty $FE40
$00001C78: rts
$00001C79: tay
$00001C7A: lda $1C92,y ;grab adjusted volume from lookup table
$00001C7D: ora #$90    ;write to all 3 volume registers
$00001C7F: jsr $1C65
$00001C82: ora #$20
$00001C84: jsr $1C65
$00001C87: eor #$60
$00001C89: jsr $1C65
$00001C8C: ldy $74     ;set to 35 by loader
$00001C8E: dey         ;horrible delay loop
$00001C8F: bne $008E
$00001C91: rts
   ;lookup table to convert linear 4-bit sample to log 4-bit sample
$00001C92: .DB $00,$00,$01,$01,$01,$02,$02,$03,$04,$05,$06,$07,$08,$09,$0C,$0F