This is a list of free/open music software
- Audacity the 'must have' sound/music app. Put it on everything.
- Oceanaudio another powerful editor
- LMMS similar to Garage Band, made to be simple for beats etc.
- Hydrogen drum machine
- MIXXX DJ software
- Sonic Pi code based synth
- Bespoke Synth modular synth
- OpenAV software has a github repo
Free Commercial software
- Here is a great article listing a lot of free commercial software.
The advanced stuff
I cant talk about electronic music without mentioning teenage engineering