Csound (I think v3) was the first music language I played with, back in the early 90s, under DOS even. Back then, running in real-time wasn't a thing. Generate a WAV file and play it after the program finished. Later, at the end of the 90s, I remember playing with CLM/CM, in common lisp.

But the most productive experience was definitely SuperCollider. I can only recommend giving it a try. Its real-time sound synthesis architecture is great. Basically works sending timestamped OSC messages AOT (usually 0.2s). It also has a very interesting way of building up so-called SynthDefs from code into a DAG. I always wondered if a modern rewrite of the same architecture using JIT/AOT technology would be useful. But I digress... SC3 is a great platform to play with sound synthesis... Give it a try if you find the time.