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.
With Family Sharing set up, up to six family members can use this app.