This is pretty durn cool: Eric Persing is a world renown synthesist that builds sound modules for Spectrasonics (I own several of the pieces he put together). Interestingly, he and a friend of mine went into business together in about '81, building MIDI interface software for the Apple ][ - I got his gig with a band called Jules and the Boys when they quit to build that business. Good times.
Anyhoo - Eric built the machine that you'll see in this link and accompanying video and demonstrated it at the NAMM show this year. It's gorgeous and a pretty neat confluence of analogue synths, 2 iPads, 2 iPod Touches and Spectrasonics software. He improvs for a while in the video - it starts to kick in nicely at about the 17:30 zone, but the improv starts at about 14:00 and is worth watching, if just to see how a master spins his own gears to get something happening.
http://www.cultofmac.com/a-marriage-of-analog-and-digital-the-moog-synthesizer-meets-the-ipad/77456Enjoy!