“Music IO: MIDI over USB allows you to send MIDI between an iOS device and a Mac, using only an ordinary USB sync cable. No camera connection kit, or other hardware — just lightning fast MIDI in both directions, using a cable you already own.
Install Music IO on your iOS device and Mac, and start the apps on both; when you connect the sync cable, the apps will detect each other automatically. After that, MIDI sent from one side will be forwarded to the other, with latency on the order of a millisecond or less.
If you need audio transfer as well, check out the Music IO: Audio and MIDI over USB (which does, as you might guess, both audio and MIDI). The Mac server can handle either type of connection, making installation easy.
For audio, there are also VST and AU plug-ins, allowing easy integration of iOS synthesizers and effects apps into a traditional desktop environment.”
Source : http://secretbasedesign.com