I don't know the music either, but it sounds quite popular...gosh..
I've just dug a bit, and that instrument has a proper name and it's "Melodica". Same family as harmonica and accordion.
The modern form has been invented and manifactured by Hohner Musikinstrumente GmbH & Co. KG, as a variation for the harmonica.
In Italy, similar instruments have been known since the 19th century, and in italian actually, it has also some other names like Pianica, Clavietta or Diamonica.
Similar to Melodica are Accordina and Vibrandoneon, make a google search on these two and you'll find very curious instruments.
Melodica
classification: free-read aerophone