Although the tone of the doorbell is not as monotonous as before, it is still different from piano. However, China's designer Li Jianye gives us a piano doorbell. This product has several piano keys which allow the guest to play what ever tone he likes.
These are not mine, but I make a different type of door bells. I call my Universal Charm door bells, "A-door-a-bells." I used to hang these on my doors like a merchant door bell that sounds whenever someone opens a shop door to come in or leave.