Virtual Instruments on your Windows Phone is a great App for the kids.
Play a variety of musical instruments Steel Drums, Flute, Electric Guitar, Piano, Saxophone, Organ, Clarinet, Trombone, Bells, Violin, Harp, Cello, Banjo, Recorder, Guitar, Xylophone.
Play using the basic musical notes of a full octave CDEFGABC.
Play freestyle ...