Alternatively you can run a DAW like SunVox on just about any smart device made in the last two decades from Windows CE and Palm to modern Android and iOS devices, as well as Linux, Mac, and Windows.

In most cases this is probably way more flexible, fully featured, easy to use, and cheaper than involving a Pi.

My current set up is a MIDI controller connected to an otherwise junk and unloved 2-in-1 laptop/tablet running Ubuntu Studio. Pretty low latency and SunVox is literally made for touchscreens and slow hardware. I love it!