Xpantastic!

The buttons on the left play basses and chords, and, on the right melody and chords. It plays 
mechanically like a normal chromatic accordion buttonnoard, but it is a MIDI keyboard. 
Advantages of a chromatic buttonboard are that it is very fast, you can play huge chords no 
matter of your hand size, and, the fingering is the same in any key, which makes tranposing 
a piece of cake.