how to get rid of ticks in audio?

[quohog]

I'm writing a little musical program where you can set the frequency, tone, and volume of notes on a timeline, and when the beat marker sweeps through, it plays the tone defined at each spot. It mostly works, but when you set the volume or distortion of one of the notes to be zero, it creates a small but annoying "tick" or "pop" every time that note is passed. I've changed the order in which I'm setting the three values, but whenever I set the volume or control to be 0, there's the tick. 

 

Here's how I'd LIKE my code to look:

    jsr GetTone
    sta AUDC0

    jsr GetVol
    sta AUDV0

    jsr GetFreq
    sta AUDF0

So simple! Right? Seems like it should work, right? But here's how I actually have it now:

 

   jsr GetTone
    beq SKIP_NOTE        ; Skip the rest or there will be a tick
    sta AUDC0
    jsr GetVol
    beq SKIP_NOTE        ; skip this or there will be a tick on the first 0 vol beat
    sta AUDV0
    jsr GetFreq
    sta AUDF0

The problem with this "fix" is that you can't actually set your notes to be zero volume. You can try, and I'll display it as a zero, but I won't actually set it because of the tick sound. So you can still hear the note playing faintly. I've created a lie.

 

I know it's hard to debug without seeing the whole thing, but its such a mess, no one should have to see it. I'm hoping someone might know some general good practice rules about setting a zero volume without creating a pop. Is there a correct order of operations to do such a thing?

 

Thanks for any insights, rules, or experience you care to share!