First thought: Cool!
Second thought: Well......yeah, people are more likely to do things that are fun. This is a "theory"?
Third thought: Sure, they'll take the stairs if the stairs are musical. They'll also dance around on the stairs, getting in the way of other people who are just trying to go up or down. That will get super annoying during rush hour, and sooner or later you're going to have people getting punched because they were playing Chopsticks while somebody was trying to get to work. Or worse, knock them down the stairs-- which would be a very musical way of getting seriously injured.
Being practical is a buzzkill sometimes.