“You should try anything once—except incest and folk dancing”

“You should try anything/everything once—except incest and folk dancing” is a popular jocular saying of unknown authorship. “His hobby is to try anything once— except fretwork and folk dancing” was written in the Who’s Who in Broadcasting (1933) entry for English author and playwright Lawrence du Garde Peach (1890-1974).
   
The saying is most frequently credited to English composer and poet Arnold Bax (1883-1953), who wrote in 1943, “A sympathetic Scot summed it all up very neatly in this remark, ‘You should make a point of trying every experience once, except incest and folk-dancing.’” English conductor and impresario Thomas Beecham (1879-1961) is also often credited with the saying, but it’s not documented if he ever said it.
 
   
Google Books
Who’s Who in Broadcasting
1933
Pg. 113:
PEACH, L. du GARDE, playwright and journalist, known to Punch readers by initials “L. du G.”
(...)
His hobby is to try anything once— except fretwork and folk dancing.
   
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The Spectator
Volume 155
1935
Pg. 320:
And that is the theory, often advanced by the unlikeliest-looking people, that one should try anything once. (“Except,” as one of our younger composers has immortally remarked, “incest and folk-dancing.”)
 
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Try Anything Twice:
Essays and Sketches

By Jan Struther
London: Chatto & Windus
1938
Pg. 2:
And that is the theory, often advanced by the unlikeliest-looking people, that one should try anything once. (“Except,” as one of our younger composers has immortally remarked, “incest and folk-dancing.”)
   
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The Spectator
Volumes 185-186
1950
Pg. 242:
But on the principle enunciated in Sir Arnold Bax’s autobiography—“anything once except incest and folk-dancing”—I went to make the acquaintance of nine new Nordic composers.
     
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Hi-fi News & Record Review
Volume 25, Issues 1-6
1980
Pg. 99:
As Walter Legge reportedly used to say of any new idea: ‘We’ll try anything once, except incest and country dancing.’
 
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City Folk:
English Country Dance and the Politics of the Folk in Modern America

By Daniel J. Walkowitz
New York, NY: New York University Press
2010
Pg. 68:
I’ll try anything once, except incest and morris dancing.
—Linzi Drew, a British stripper (also attributed to Oscar Wilde, Sir Arnold Bax, Sir Thomas Beecham, and George Bernard Shaw, among others)
 
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The Dictionary of Modern Proverbs
Edited by Charles Clay Doyle, Wolfgang Mieder and Fred R. Shapiro
New Haven, CT; Yale University Press
2012
Pg. 128:
One ought to try everything once except incest and folk dancing.
1943, Arnold Bax, Farewell, My Youth (London: Longmans, Green), 17: “The folk-song phase was inevitably followed by an enthusiasm for folk-dancing, and as to this infliction I, for one, would have been happy to cry: ‘The nine men’s morris [dance] is choked up with mud.’ A sympathetic Scot summed it all up very neatly in this remark, ‘You should make a point of trying every experience once, except incest and folk-dancing.’”
1972 Wall Street Journal 17 Aug.: “When George S. [Kaufman] was a very young boy, his father told him to ‘try everything in life except incest and folk dancing.’ He did.”
Yale Book of Quotations Bax, The proverb originated as an anti-proverb based on “You should try everything (anything) once.”