Just a blatant plug for our new synth which has just hit the Apple store:
https://itunes.apple.com/WebObjects/MZStore.woa/wa/viewSoftware?id=1011132019
It uses our Equator sound engine internally, and the new Apple force-touch screens provide a nice playable on-screen keyboard. The engine uses our new MPE and synthesier classes, and can work with a bluetooth RISE controller.
Check it out, it's a really cool synth (and FREE!)