The extension point also brings a full audio plug-in model to iOS and lets you sell Audio Units on the App Store. The Audio Unit extension point allows your app to provide musical instruments, audio effects, sound generators, and more for use within apps like GarageBand, Logic, and other Audio Unit host apps.
There had been some rumors about that since Monday (the start of the WWDC). I was already quite excited about that one, but I just discovered an Apple demo code for another feature, which might render this usage of multitasking useless again. This is going to be quite useful if you want to control two synth apps at the same time, or if you want to record a synth app in a DAW app. The first one is multitasking which will allow us to use two apps at the same time. The upcoming iOS 9 update seems to have some exciting features for us musicians.
