OK but
There are several different sounds. The timbre on all of them is good. However, the attack and decay are very abrupt. i.e. the sound very sharply turns on and off. It would sound nicer and more like a real instrument if the sound had a smoother rise and fall when each note begins and ends. Also, I could not play it quickly and smoothly - perhaps this is a trouble with with the iphone? I only bought my iphone one week ago.