Honestly, I'm amazed that smartphones haven't given rise to a ton of people using trackers or synths and whatnot. I remember going and looking on F-Droid and being a bit surprised that there was limited tracker software, often ports of old stuff.

Okay, you need headphones, but it seems like the kind of thing that generally, one could do in bursts while riding mass transit or waiting in line or whatever, and where smartphone hardware isn't a really limiting factor.