It’s a forest xylophone! This is a Japanese commercial that the kid asked to watch three times in a row. The music played on the custom-made wooden keys of this beautiful instrument: Jesu, Joy of Man’s Desiring, from Cantata 147 by Johann Sebastian Bach.
2022 Update: See it on display in Japan.
Then watch Boomwhacker Bach: Prélude n°1 aux tubes musicaux next.
via Science for All.