“What do you get when you drop a piano down a mine shaft?” (joke)

A popular piano joke is:
 
Q: What do you get when you drop a piano down a mine shaft?
A: A flat miner.
 
The “miner”/“minor” pun has been cited in print since at least 1975.
 
“What do you get if you drop a piano on a child?”/“A flat minor” and “What do you get when you drop a piano on an army base?”/“A flat major” are related jokes.
 
 
14 March 1975, Ennis (TX) Daily News, “Ennis Echoes” by Casey, pg. 1, col. 1:
What happens if you drop a piano down a mine shaft? You get A Flat Minor.
 
Newspapers.com
14 May 1975, Newhall Signall & Saugus Enterprise (Santa Clarita, CA), “Friendly Valley Report: Off-Beat Competition” by Stu Wilson, pg. 19, col. 1:
What happens if you drop a piano down a mine shaft? You get A Flat Minor! (Sorry about that!)
 
16 April 1976, The Daily Review (Hayward, CA), “Jaborrocky” by Ray Orrock, pg. 17, col. 1:
Latest riddle among the skateboard set:
 
Q: What note do you get when you drop a piano down a mine shaft?
A: A flat miner.
 
Google Books
The Crack-a-Joke Book
Harmondsworth, England: Penguin Books
1978
Pg. 125:
What do you get when a piano falls down a mine ?
A flat miner.
 
Google Books
February 1981, Boys’ Life, “Think & Grin,” pg. 74, col. 2:
Beethoven: What do you get when you drop a piano down a mine shaft?
Mozart: A flat miner. — Brent Morrow, Independence, Mo.
 
19 July 1985, Greensboro (NC) News & Record, “Bad jokes: The worst was best” by Susan Ladd, pg. B1, col. 4:
What do you get when you drop a piano down a mine shaft?
A flat minor.
—Cedric M. Alston, 11 1/2
High Point
 
Google Books
Smart Alec’s Revolting Jokes for Kids
By Ward Lock & Co., Ltd.
New York, NY: Ballantine Books
1989, ©1987
Pg. 10:
What do you get if you drop a piano down a mine shaft?
A flat miner.
 
Google News Archive
3 November 1990, The Blade (Toledo, OH), ‘Personals” by Leah Garchik, The Peach, pg. 1, col. 1:
What do you get when you drop a piano down a mine shaft? A flat miner (Jackie Pels of Walnut Creek).
   
Google Books
The Mammoth Book of One-Liners
By Geoff Tibballs
London: Constable & Robinson Ltd.
2012
Pg. ?:
What do you get when you drop a piano down a mine shaft?
A flat miner.