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 StoreAudiobus is the app that makes the rest of your setup better.
Does any voice harmony app modify scale via MIDI input?
I have a TC Helicon pedal which listens to the guitar input, detects chord played, and in real time updates the harmonies applied to the voice input. This is a great feature for any song that modulates away from the original key.
I've suggested this update a year ago to the developers of Harmony Voice, iVoxel, VoiceLive, etc. I think it would be great.
Is there another app that does this? I was thinking one would use MIDI rather than guitar to set harmony key to avoid requiring two audio input channels.