heres how one way to make sound on N64 :
Crazy nation trainer  (xtremeG version)

   
     [we tested button and its time to make sound!]
       lui     $t4,8031       ;make pointer to 'yes' sound
       addiu   $t4,$t4,4F10   ;80314f10 = start
       addiu   $t5,$zero,4A71 ;4A71=length
       addiu   $t6,$zero,1388 ;1388= DAC rate
       addiu   $t7,$zero,0001 ;1=BIT rate
       jal     here
       nop
    [draw yes]
......

   [we tested button and time to make 'no' sound]
         lui     $t4,8031        ;make pointer to 'no' sound
         addiu   $t4,$t4,12C4    ;803112C4
         addiu   $t5,$zero,3C45  ;3C45=length
         addiu   $t6,$zero,1388  ;DAC rate
         addiu   $t7,$zero,0001  ;1=BIT rate
         jal     here
         nop
    [draw no]

.....        
         [...initialize vid, audio]
           addiu   $t4,$zero,0000  ;[blank out sound]
           addiu   $t5,$zero,0000  ;initialize
           addiu   $t6,$zero,0001
           addiu   $t7,$zero,0001
here:      lui     $t8,A450
           sw      $t4,0000($t8)  ;start RDRAM address
           sw      $t5,0004($t8)  ;length
           addiu   $t9,$zero,0001 
           sw      $t9,0008($t8)  ;1 = enable dma
           sw      $t6,0010($t8)  ;dac rate 
           sw      $t7,0014($t8)  ;bit rate 
           jr      $ra
           nop