I’ve been using a new extension that doesn’t generate JavaScript - it generates MakeCode Arcade images that it will parse using an easy-for-a-robot-to-generate-but-not-easy-for-humans-to-make format. So it’s easier to copy and paste a bunch of images into an image editor than to switch to JavaScript, create a new .ts file, paste in JavaScript, pray to the gods of MakeCode Arcade and switch back to blocks hoping nothing has been screwed up.
The extension is here:
I’ve written a Python script to take a MIDI file, do some mediocre black magic, and generate okay images:
You can find the code and instructions in the repo. Python knowledge is highly recommended for installation as the instructions won’t go over every single command to install.
It’s pretty good with songs that have a consistent beat - it’s absolute garbage with triplets and weird rhythms. And rests don’t exist! I’ve worked on this for several months and it doesn’t want to work with rests and stuff so PRs are welcome. 
For performance on actual hardware, I have not tested it thoroughly, I’ve only tried it on small images in one of my games on a PyGamer which seemed to be fine.