lda  #0
     ldx  #%00001111
@    sta  screen+0*40,x
     sta  screen+1*40,x
     sta  screen+2*40,x
     sta  screen+3*40,x
     dex
     bpl  @-

     lda  trackn_volume; kanał 0
     lsr  @
     lsr  @
     lsr  @
     lsr  @
     tax
     lda  #47 ; znak O
@    sta  screen+0*40,x
     dex
     bpl  @-

     lda  trackn_volume+1; kanał 1
     lsr  @
     lsr  @
     lsr  @
     lsr  @
     tax
     lda  #47 ; znak O
@    sta  screen+1*40,x
     dex
     bpl  @-

     ...