Genesis Game crashes with 2 additional lines of code in the sound driver

Hi,

I'm trying to make it so if d0 is 0, the music is not looped, while if 1 it will loop repeatedly. Here is the original code:

Code:

;==============================================================   
;ComradeOj's simple VGM player.
;Plays music from Shiru's VGM MM; no PCM.
;==============================================================
music_driver:
        move.l a2,-(sp)
        move.l d4,-(sp)
        move.l vgm_current,a2
vgm_loop:       
        clr d4
        bsr test2612
        move.b (a2)+,d4
        move.l a2,vgm_current
        cmpi.b #$61,d4
        beq wait       
        cmpi.b #$66,d4
        beq loop_playback
        cmpi.b #$52,d4 
        beq update2612_0
        cmpi.b #$53,d4 
        beq update2612_1
        cmpi.b #$50,d4
        beq update_psg
        bra vgm_loop
   
update2612_0:
        move.b (a2)+,$A04000
        nop
        move.b (a2)+,$A04001
        bra vgm_loop
       
update2612_1:   
       move.b (a2)+,$A04002
        nop
        move.b (a2)+,$A04003
        bra vgm_loop
       
loop_playback:       
        move.b #$9f,$c00011
        move.b #$EF,$c00011    ;kill psg
        move.b #$FF,$c00011       
        move.b #$BF,$c00011
        move.l vgm_start,a2
        bra vgm_loop
       
update_psg:
        move.b (a2)+,$C00011
        bra vgm_loop
   
wait:
        move.l (sp)+,a2
        move.l (sp)+,d4
        rts

test2612:
        clr d4
        move.b $A04001,d4
        andi.b #$80,d4
        cmpi.b #$80,d4
        beq test2612 
        rts     

While here is my modified code:

Code:

;==============================================================   
;ComradeOj's simple VGM player.
;Plays music from Shiru's VGM MM; no PCM.
;==============================================================
music_driver:
        move.l a2,-(sp)
        move.l d4,-(sp)
        move.l vgm_current,a2
vgm_loop:       
        clr d4
        bsr test2612
        move.b (a2)+,d4
        move.l a2,vgm_current
        cmpi.b #$61,d4
        beq wait       
                 tst d0
                 bra.s skip_vgmloopplayback
        cmpi.b #$66,d4
        beq loop_playback
skip_vgmloopplayback:
        cmpi.b #$52,d4 
        beq update2612_0
        cmpi.b #$53,d4 
        beq update2612_1
        cmpi.b #$50,d4
        beq update_psg
        bra vgm_loop
   
update2612_0:
        move.b (a2)+,$A04000
        nop
        move.b (a2)+,$A04001
        bra vgm_loop
       
update2612_1:   
       move.b (a2)+,$A04002
        nop
        move.b (a2)+,$A04003
        bra vgm_loop
       
loop_playback:       
        move.b #$9f,$c00011
        move.b #$EF,$c00011    ;kill psg
        move.b #$FF,$c00011       
        move.b #$BF,$c00011
        move.l vgm_start,a2
        bra vgm_loop
       
update_psg:
        move.b (a2)+,$C00011
        bra vgm_loop
   
wait:
        move.l (sp)+,a2
        move.l (sp)+,d4
        rts

test2612:
        clr d4
        move.b $A04001,d4
        andi.b #$80,d4
        cmpi.b #$80,d4
        beq test2612 
        rts     

The music plays but, the game crashes right after the song finishes regardless of wither d0 is 0 or 1. Any assistance in this matter would be greatly appreciated.

Sincerely,

Scorpion Illuminati