The following demonstration shows the making of a Trance loop using an iPad app called SoundPrism Pro to control a Nord Lead 3 via midi connection.
Download the audio performance loop of from this video at
http://ipadloops.com/freee-loops/soundprism-nord-trance-pad.zip
SoundPrism Pro is a MIDI Controller for iOS based on the popular SoundPrism App for iPad and iPhone. SoundPrism Pro supports Core MIDI via a wireless connection or USB via the Camera Connection Kit made by Apple (USB is iPad only).
SoundPrism Pro is available for $15.99