If you’d like to learn computer music, I would start with pure data. There are a series of 30-some youtube tutorials that walk you through pretty much the entire language, by a university professor. Pure data is free, open source, graphical programming language. Its very easy to pick up w/ tutorials.
Supercollider has a pretty massive learning curve but if you know any written languages it may be easier for you than it was for me. It’s much more powerful than pd, and if you put the time in you can make some aweomse sounding material.
MAX is just pure data for $600.
If you want to simply start playing music you can send midi to Ableton, Garage band? or AU Lab ?(free w mac).
Hope this helps!