One of the reasons I really enjoy iOS for making music is the fact that it is so easy to make music with an alternative interface/design. I ran across a new one today that I thought I would share with you.
Temperament provides you with a nifty three circle design giving you the chromatic scale on thirteen circles with each ring going one octave higher. Simple and yet effective. Even better is the fact that it is not a piano keyboard. Not many options for built in sounds and no option for MIDI control to a different app currently. Maybe the developer will keep adding more options in the future.
There are options though for adjusting what happens when you move your finger on the X or Y axis.
Just fun to play with. Free too.