Bookmark dump. Sadly I haven't had time to dig into many of these.

Overtone (clojure) for music https://overtone.github.io/

Bauble https://bauble.studio/about/

Nannou (rust) https://nannou.cc/

Quil (clojure) http://www.quil.info/

Open Frameworks (C++) https://openframeworks.cc/

p5.js is a JavaScript library that I've enjoyed messing with. It's related to Processing.

https://p5js.org/

I will second p5/processing as a fun tool. It's really a pretty easy and way to get into generative art. P5.js has an online editor which makes it easy.

The new nature of code book was updated to use p5 instead of processing and a fun way to start. As is the "coding train videos" which are interesting in the seem for kids but cover more advanced topics..

https://natureofcode.com/

https://youtube.com/@thecodingtrain?si=dmjxLScgm9Wdi4sV

I used p5.j5 to merge DNA sequences and my photographs. People seem to like them ( they've been accepted to jurrored shows)

I make they layers in p5 then manipulate in gimp.

I put some online: https://aramcomjean.smugmug.com/DNA-is-Just-Part

I got really into OPENRNDR for a while, I really enjoy working with it.

https://openrndr.org/

Checkout out this list: https://github.com/terkelg/awesome-creative-coding

Check Touch Designer.

For 2D output, Postscript and especially MetaPost are useful.