Chico's yes...because he tickled the ivories in such a fun, playful way and frankly, his fingers and facial expressions are always a joy to watch.
Harpo's solos are quite serious, beautiful as instrument as it is, there's really no way to liven up a harp.
But then again...had these interludes NOT been included in the movies then none of us would ever know what gifted musicians Arthur and Leonard Marx were!!
Apple
ps - I always loved the I Love Lucy episode where Harpo & Lucy revamped that mirror bit from Duck Soup!!