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.
Sirens' Chor - Synth Chorus by Aleksandar Mlazev
https://apps.apple.com/app/id1497361812
Audio Unit V3 synth chorus efx
Description:
This one is quite experimental and CPU heavy app!
While working on my Chord Detector app I came up with the idea to play the found harmonics with sine wave oscillators so I can hear what the algorithm is hearing 
It turns out to be an interesting output that led me to creation of this audio effect app.
What happens here is that the input is analysed for main harmonics in the range of 80Hz to 1500Hz. Then a series of sine wave oscillators are set to play those harmonics with the exact frequency and volume and their output is added to create a second voice. This second voice can then be mixed with the input to create some kind of chorus or played alone. All this is CPU heavy process so it should be used with care...
Also to make this effect possible I had to use limited range 80Hz to 1500Hz so it is not suitable for every instrument and you have to keep that range in mind when producing.
Some very fast volume and frequency changes are applied to the oscillators.
The app is AUV3
Comments
Video:
Anyone has tried it?