The Movement I-V is a unique musical instrument created by the sound artist Espen Sommer Eide (Alog, Phonophani). It explores the various possible movements of the hand and the fingers in sound manipulation. Included are a set of sounds by the artist. You can also upload your own samples in .wav or .aif format through iTunes.
The effect that you apply to the samples draws inspiration from vintage analog tape echo machines, so each of the circles (moved by your fingers) represent a moving tapehead, and crossing the middle line play the sample backwards or forwards.
Each of the circles also have its own base pitch, that can be changed in the pitch-change mode.
A video of the app in action can be found at: http://sommer.alog.net/pages/45
Important noticw for ios 5 ipad 2 users. Turn off multitouch gestures in system preferences before using this app.