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.
Demo of Zvon soundfonts in Gestrument Pro (2nd video added)
I am using 2 of the excellent Gestrument Pro factory presets to showcase some of the soudfonts that I have created over the years.
My sounds heard are form the Marching Band Horn and the mobile versions of Julie Resynth ($2), the Prepared Electric Piano ($1.99) and the Chromatic Hits ($3.99) soundfonts that are smaller and cheaper versions of larger sets.