I've been making a DSL for writing sheet music specifically for drums as raw text, inspired by ABC Notation (but of course just for drums).
Now writing this I noticed that it's kind of complicated to explain and having a landing page would make my life so much easier.
But the gist of it is, you write notation that looks like this: https://gist.github.com/Luigi123/945af7e5cc8dfbfd186f0a99754... and it renders sheet music in PDF, and also allows you to play the same music as a game (DrumMania / DTXMania style).
Now the language / compiler itself has been working quite well and I've been dogfooding it for like six months now. The next thing is an IDE-style editor where you can import a song and write the notation following it. Making THAT has been quite the journey. Here's a screenshot for good measure: https://i.imgur.com/EmlqlrM.png