Groucho's my favorite Marx brother, as you know, but that's nothing against Harpo. I just happen to prefer say-funny to do-funny, and Harpo did funny as well as any before or since. And if others could get bigger laughs, none of them could play like Harpo could.
Here he is in Horsefeathers, performing the movie's theme "Everyone Says I Love You." (Elsewhere in the film he whistles it to a horse.)
Fourteen years later, if memory serves, he performed Liszt's Second Hungarian Rhapsody in A Night in Casablanca. MeTubers will remember this melody as sung by Daffy and lip-synched by Jar Jar back in the day.
Finally, here's a tribute to his talents, sung by Jonathan Richman over footage from Monkey Business.