Midi player on Pi4
I have recently added an article to the site detailing a program which enables Sonic Pi to play Midi Files. There are two versions: one uses a TouchOSC interface running on a table ort phone to control the process, the other simpler one works directly, but you have to specify synths in advance.
rbnrpi 
I haven’t been using Sonic Pi for the last couple of years, but, today I resolved to start using it again. Thanks for the article Robin.
Glad you enjoyed it. Just note that if you want to use it on a Pi4 or Pi3B with latest Raspbian Buster, then you will at present have to build your own version of Sonic Pi. The one provided in the distribution does NOT support Midi or OSC. You either need to use version 3.0.1 on Raspbian Scratch on a Pi3 or build your own from source on a Pi4, which is not too difficult to do. See article at here