Audiobus: Use your music apps together.
What is Audiobus? — Audiobus is an award-winning music app for iPhone and iPad which lets you use your other music apps together. Chain effects on your favourite synth, run the output of apps or Audio Units into an app like GarageBand or Loopy, or select a different audio interface output for each app. Route MIDI between apps — drive a synth from a MIDI sequencer, or add an arpeggiator to your MIDI keyboard — or sync with your external MIDI gear. And control your entire setup from a MIDI controller.Download on the App Store
Audiobus is the app that makes the rest of your setup better.
Ability to "break out" separate internal instruments onto separate "sub-channel" mix-busses
I've been loving using NAVICHORD to send MIDI to SOUNDPRISM Link Edition in AB3.
AB3 compatible Apps like SOUNDPRISM can receive MIDI separately now - for each or any of its internal instruments ( EG Bass, Chord, Melody ).
However the volume cannot be adjusted independently for each of the 3 instruments - just a single mixer fader.
It would be uber-cool if in a future AudioBus 3 API it was possible to break out the individual instrument output channels to separate faders - so in the MIXER page there would be (optionally) an individual fader for SoundPrism (BASS) another for (CHORD) and another for (MELODY).
Clearly this is some sort of Multichannel out API - as opposed to stereo.
Such a feature would also clearly be very useful for when hosting Gadget.