There is nothing like playing the piano. There is a very real tactile resonance as the hammers thump and the music resonates across your body. The depth, weight, texture and feel of the keys on your fingers as the notes reverberate up your wrists is nothing less than magical. Even the highest-end electronic keyboards cannot duplicate this experience. There's nothing like real thing.
A video game cannot replicate this experience.
True musicians may find Rock Band entertaining, a fun test of your timing and coordination. But any real musician will tell you that it is little more than a glorified timing game. Rock Band is not music. But it is close enough to the real thing to deliver an "authentic" experience to the unexperienced.
Wii Music further removes the realism from the experience. While Guitar Hero at least allows players to believe they are holding a guitar, Wii Music requires that users pretend to be holding an instrument. While Rock Band allows user to strum and feel the flick and feedback of the "strings", Wii Music allows you do play air guitar like never before.
To quote a friend from college - everyone feels cool holding an electric guitar. One foot foward, one hand sliding down the long neck, even while strumming nonsensically with an overbearing amount of overdrive distortion - you just feel like a Rock Star.
Air guitar isn't fun after two or three minutes.
So where's the appeal in Wii Music?
Are these two scenarios remarkably similar, or am I crazy?