Recommended and mentioned products
Make music with a free, cross-platform tool
SunVox is a small, fast and powerful modular synthesizer with pattern based sequencer (tracker).
A free, easy to use tool for creating music.
BoscaCeoil, https://boscaceoil.net/ is a light weight, simple, and easy tool to create music, for sound effect bfxr, https://www.bfxr.net/ is a good choice.