A popular viola riddle is:
 
Q: What’s the difference between a viola and a coffin?
A: The coffin has the corpse on the inside.
 
The joke has been cited in print since at least 1993.
   
 
Google Groups: rec.arts.marching.misc
Lots of Music Jokes
.(JavaScript must be enabled to view this email address)
6/21/93
(...)
What’s the difference between a viola and a coffin?
The coffin has the dead guy on the inside.  [JCB]
 
Google Groups: rec.music.classical
Classical Music Jokes
Robert Bratulic
2/14/94
(...)
What’s the difference between a coffin and a viola?
The dead man is inside the coffin.
 
31 March 1994, New York (NY) Times, “Offstage With: Cynthia Phelps; Playing the Tune and Calling It, Too” by James R. Oestreich, pg. C1, col. 3:
Or perhaps it comes from the fact that her instrument gets no respect. At a time when excellent young violists seem to be everywhere, viola jokes (What’s the difference between a viola and a coffin? The coffin has the corpse on the inside.) have made their way from orchestral circles to a broader musical public.
 
Google Groups: rec.music.classical.performing
Viola Jokes
Pete
4/6/95
(...)
What’s the difference between a Viola and a coffin?
The coffin has the corpse inside.
 
Google Groups: rec.humor
canonical list of viola jokes
John Casten
5/31/95
(...)
What’s the difference between a Viola and a coffin?
With a coffin the dead person is inside.
 
Google Books
A Prairie Home Companion
Pretty Good Joke Book (3rd Edition)
By Brian Becker
Minneapolis, MN: HighBridge
2003
Pg. 186:
What’s the difference between a viola and a coffin?
The coffin has the dead person on the inside.
   
Google Books
The Ultimate Book of Jokes:
The Essential Collection of More Than 1,500 Jokes
By Scott McNeely
San Francisco, CA: Chronicle Books
2011
Pg. 151:
What’s the difference between a viola and a coffin?
The coffin has a dead person on the inside.
 
Google Books
Killing Yourself to Survive:
Stories
By David Corbett
Open Road Media (MysteriousPress.com)
2012
Pg. ?:
What is the difference between a coffin and a viola? With a coffin, the corpse is on the inside.
 
Twitter
John Brookfield
‏@MeltHell
What’s the difference between a viola and a coffin? The coffin has the dead person on the inside. http://fxmb.info/M4lNCJ  #jokes
10:06 PM - 20 Aug 2016