Live coding - real time programming to compose, play music or design animations (opens in new tab)

And not as a quote! That is amazing.

Take a look at ChucK's baby brother 'miniAudicle' if you just want to try the water. It's fun ... you'll have sound in a couple minutes! http://audicle.cs.princeton.edu/mini/

For a book on theory try "Computer Music" by Dodge & Jerse. The Curtis Roads books are v.good too.

I'd just get started improvising with whatever! and then as you get time, check out the (many!) software options and see what fits your mental/musical personality. It's always a battle not to get over-lost in the tech side at first because that can cramp your creativity ... and even your motivation.

Finally, for a DEEP course in EM try The CSound Book. CSound will let you make ~any sound you can conceive ... but it's a heavy lift. (More for studio than live.)

I have played music with Processing, Python (a cool thing called Midi Musical Accompaniment or MMA), Chuck, Lily for Firefox, and Max with some of the Monome stuff... A lot of it is done with Open Sound Control (OSC) behind the scenes sending UDP around and connecting the disparate parts. I would say just dive in!!!!