Aum
Aum is a fantastic music/audio tool for ios.
It works like a mixer. You can have as many channels as you want. Channels can be audio or midi. Each audio channel can take audio from an input, or an IOS app, and can send to the output or another channel. Each channel can be configured with pre and/or post fader sends which can send to other channels, or to AUv3 effects.
It's an incredibly well designed and flexible app.
