Isn't this useful! "This is what our teacher taught us on the last day of French class. Did I mention she’s awesome?" // Not actually a school idea (never ever), but it's French so I'm putting it here.
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.