Entry in progress—B.P.
“It’s the silence between the notes that makes the music.”
“It’s the notes you don’t play that matter.”
   
Wikipedia: Claude Debussy
Achille-Claude Debussy (22 August 1862 – 25 March 1918) was a French composer, prominent in the style commonly referred to as Impressionist music, though he himself intensely disliked the term.
 
Sourced
Music is the space between the notes.
. As quoted in Turning Numbers into Knowledge: Mastering the Art of Problem Solving (2001) by Jonathan G. Koomey, p.96 ISBN 0-9706019-0-5
. Unsourced variant: Music is the silence between the notes.
 
Google Books
Domenico Scarlatti
By Ralph Kirkpatrick
Princeton, NY: Princeton University Press
1953
Pg. 308:
The essential expressive quality of a melodic interval lies not in the notes themselves but in the space between the notes, in the manner in which one gets from one note to another. The assumption that musical value lies in the notes themselves and not in the transition from on to another is the prime heresy of the keyboard player.
 
OCLC WorldCat record
The space between the notes : rock and the counter-culture
Author: Sheila Whiteley
Publisher: London ; New York : Routledge, 1992.
Edition/Format:   eBook : English
 
OCLC WorldCat record
The space between the notes
Author: Richard A Wing
Publisher: Mobile, Ala. : HB Publications, ©1994.
Edition/Format:   Book : English : 1st ed