Audiobus is a very handy little app that has served many iOs users well, and it is now free!
https://itunes.apple.com/app/audiobus/id558513570
It supports over 750 apps! Including, but not limited to, some great apps like:
- GarageBand
- Animoog for iPadAlchemy
- all KORG apps
- Rebirth for iPad
- Figure
- Cubasis
- BeatMaker2
tl;dr
If you make music on iOS, DL this app, for your health.