You’ve got the resonance of filter 2 cranked all the way up. You also have 4 voices playing, all oscillators turned up to max, amps and levels turned to max. I’m not sure what else you expect. You’ve basically put everything as loud as you can, and then you are massively boosting a frequency range, and sweeping it. I would think that some distortion occurring would make total sense in this scenario. The only way the A4 could deal with this is if the overall headroom was tweaked to allow for this kind of setup, which would make a single voice with no resonance even weaker than they are now.
This is basic gain staging, there is no problem here, I would suggest you turn down the individual oscillators levels, the Amp levels, if you’re set on keeping max resonance on filter 2. It will not only fix the distortion, but also potentially save your ears / speakers from getting fried :slight_smile:

Cheers !

PS : the recommended oscillator level for minimal filter distortion is around 60, so anything above that is already introducing harmonics. You can clearly hear it with a triangle wave and a bit of resonance on filter 1.