Henry Lowengard, developer of Droneo, has released PolyHarp! Henry is an Autoharp aficionado and has spent at least the last 4 years building up an app to meet his needs. This is basically a highly customizable Omnichord, but with the added capability of exploring microtonal tunings. PolyHarp arrives with Audiobus 3 and Inter-App Audio.
PolyHarp iTunes Description:PolyHarp is a virtual musical instrument and a thought experiment.
It takes the basic idea of a chorded zither and extends it to large numbers of chord choices, made out of any kinds of intervals, multi-string courses, fretting, and massive polyphony. It's a testbed for harmonic theory as well as a great multi touch simulator of the good old "idiot zither" you have in the attic. It can ignore the microtonal aspect of the sounds to make an interesting alternative MIDI controller as well.
PolyHarp supports Audiobus 3, including saving setups, and IAA.
PolyHarp seriously needs a demo video, so I'm embedding this prototype demo from July 2014. You can watch how he constructs the harp's layout, and then hear the results at around the 2 minute mark. Over on Henry Lowengard's YouTube channel you'll find more videos about his collection of Autoharps.