Maria - thanks very much! I'll check out those links.
I know a lot of math, and I like to think I have some musical taste, but I'm really ignorant about the best way to, say, improvise on a keyboard, create a MIDI file, then edit this, then play it on some electronic instrument and record it, then do sound processing like adding reverb and other effects. I'd also love to be able to whistle or sing and have that converted to MIDI. I'd like a system that's easy for beginners but could keep being extended as I get better. I'm a bit scared to buy [Ableton](https://www.ableton.com/en/) or [Cubase](https://www.steinberg.net/en/products/cubase/start.html). So, it would be good to talk to people who would enjoy trading these music skills for mathematics.