LSDJ (little sound DJ) is a tracker for the gameboy designed for live use. It's PAYWARE.

compatibility with various gameboy models exists (GBA, monochrome gameboy and color gameboy) It's a paid tool, but demo releases are provided in ROM form so that you try on an emulator before you buy a cartridge.

Also having a "huge" ammount of peers willing to help you with mods, effects, and little tricks here and there.