Then you’re probably all set with Dirtywave, but you could also be interested in looking at SunVox for Android. It’s a combination of a modular synth, tracker and sequencer. Has a rather peculiar interface, and has been around on portable platforms like PalmOS for twenty years.

I’m not sure that the app can currently be bought, since the author is in Russia and will certainly not receive the money (not right away, at least), but afaik one can pay him directly and he’ll arrange the apk.

For my taste, SunVox is too much in beep-boop territory, so I prefer desktop trackers with some gnarly samples and effects, but the app is definitely good.