The ShakeGuitar is an interactive music system for use with iPhone/iTouch that enables users to enjoy the simulated experience of guitar playing, even if they are musical novices.
Shaking the iPhone/iTouch with varying degrees of strength influences the level of guitar-melody difficulty, which smoothly changes in real-time from soft backing to heavy soloing.
You can set each level thoughout the music by touching or draging on the level control panel.
 

The ShakeGuitar is based on a melody morphing method developed by Masatoshi Hamanaka.
Further information can be found at
http://gttm.jp/hamanaka/en/shakeguitar/