These guys are amazing musicians. Harpo doesn't play the piano, he plays with it!, he is amazing, just watch as he "shoots" the top notes with his finger. If anyone has seen Animal Crackers, their funniest movie in my opinion, you will see his prowess on there as well, simply brilliant musicians and I love their play on words humour.
Here is Chico on the piano in Animal Crackers, watch those fingers...Superb!!