In the interest of helping out people with GBJam audio as much as possible, I thought I'd share some helpful links!
- SFXR is a pretty sweet SFX generator capable of making basic, chippy sounds for your game. Any sounds you create with it are yours to keep!
- BFXR is a beefed-up version of SFXR. As with SFXR, you hold the rights to whatever sounds you create!
- Here's a list of stuff for making chiptune music created by Chiptunes = WIN. Aside from trackers and DAWs, it also has free & paid plugins you can use in any audio workstation you like.
Good luck! :D