Amiga sound power HOUSE!! YEAH!!! Seriously though, you would control the gains on your analog DJ mixer usually.
With the simultaneous keyboard issue, I wrote a small application which shows lines on screen when keys are pressed. We were unable to find an adequate place for the 4 channel mutes to go as they need to be all together. Maybe we'll do some digging soon to see what can be done.
Fired up the code today for the first time since Revision. Currently trying to battle out the Kickstart 1.2 / 1.3 bug for now. If anyone wants to help, surf over to the coders sections of the forum.