“The audience never goes out humming the scenery” (musical theatre adage)

“The audience never goes out humming the scenery” (or, “You can’t hum the scenery”) means that, while a musical might have wonderful scenery, its success lies in memorable music. The musical Camelot (1960) was not a critical success; a popular quip was “You walk out whistling the scenery.”
 
It’s not known if the “whistling/humming the scenery” line pre-dates Camelot, but it was called “an old Broadway gag” by Broadway columnist Dorothy Kilgallen in 1962.
 
       
26 March 1961, Springfield (MA) Sunday Republican, “Music for Everybody” by Sigmund Spaeth, pg. 11C, col. 7:
The most quoted comment on “Camelot” is that “you go out humming the scenery.”
 
16 June 1961, Nevada State Journal (Reno, NV), “On Broadway” by Walter Winchell, pg. 4, col. 7:
Ross Hunter is the latest to get mentioned as the author of “I came out of ‘Camelot’ humming the scenery.” That one has gotten scads of mileage since the show premiered.
 
4 December 1962, Trenton (NJ) Evening Times, Dorothy Kilgallen’s “Voice of Broadway,” pg. 25, col. 4:
ROLF GERARD has been signed to design the sets for the Vivien Leigh musical, “Tovarich,” so the composer had better watch out if the audience may go out humming the scenery, to revive an old Broadway gag.
 
Google Books
Listen Here!
A critical essay on music depreciation
By Vernon Duke
New York, NY: I. Obolensky
1963
Pg. 275:
To get back to the new producers and a very old joke, they’ll let you whistle the scenery, for all they care; their motto seems to be, “No song hits, no errors, long runs.”
 
28 April 1968, The Pharos-Tribune & Press (Logansport, IN), “Sinatra Gave Hope $5,000” by Jack O’Brian, pg. 4, col. 5:
The new “I’m Solomon” musical seemed to want to jazz up the Bible but it’s no “Hello, Solly!” more perfunctory than entertaining…Beautiful sets (by Reuben TerArutunian) but as the fella said several decades ago, you can’t walk out whistling the scenery.
 
Google Books
6 May 1985, New York magazine, “Theater” by John Simon, pg. 91, col. 1:
WE VE ALL HEARD THE ONE ABOUT THE musical you leave humming the scenery; well, Big River is the one from which you emerge hurrahing the sets.
 
New York (NY) Times
THEATER; ‘Camelot’s’ Melodious Score, Revisited
By ALVIN KLEIN
Published: November 10, 1991
OF “Camelot,” someone once remarked, “You walk out whistling the scenery.” And given its original inordinate length, this is the show that was dubbed the “Gotterdammerung” of musicals—without the laughs. There’s even a near-immolation scene toward the end, except that Lancelot appears just in time to rescue Guenevere from the stake.
 
22 December 2004, Salt Lake Tribune (Salt Lake City, UT), “A ‘Phantom’ only phanatics could love” by Sean P. Means, pg. D4:
Schumacher, cribbing a bit from Baz Luhrmann’s “Moulin Rouge,” almost single-handedly overturns the old Broadway axiom that audiences can’t hum the scenery.
 
Google Books
The Great American Book Musical:
A manifesto, a monograph, a manual
By Denny Martin Flinn
New York, NY: Limelight Editions
2008
Pg. 50:
“When you leave the theatre humming the scenery,” a knowledgeable theatre insider once said, “the show’s in trouble.”
     
New York (NY) Times
David Mitchell, Broadway Set Designer, Dies at 79
By WILLIAM GRIMES
Published: October 4, 2011
David Mitchell, whose exuberant designs for the Broadway musicals “Annie” and “Barnum” earned him Tony Awards for set design, died on Monday in Los Angeles. He was 79.
(...)
His sets for “Annie,” contrasting the grim reality of New York during the Depression with the opulence of the Daddy Warbucks mansion, played a major role in the show’s success. “If ever that old joke about leaving the theater humming the scenery was justified, this could be the occasion,” Clive Barnes wrote in his review of the musical in The Times.