Entry in progress—B.P.
“Music is the space between the notes.”
“It’s the notes you don’t play that matter.”
     
16 September 1990, Rocky Mountain News (Denver, CO), “Big wisdom comes in little package” by Margaret Carlin:
Sift with reflection: It is the silence between the notes that makes the music
 
Google Books
The Shift:
Taking Your Life from Ambition to Meaning
By Wayne W. Dyer
Carlsbad, CA: Hay House, Inc.
2010
Pg. 18:
There’s a Zen proverb that reminds us that it’s the silence between the notes that makes the music. Without silence to interrupt the sounds, there can be no music—it would be only one long, continuous tone. But of course even the long tone originated in the void.
 
Google Books
Music Medicine:
The Science and Spirit of Healing Yourself with Sound
By Christine Stevens
Boulder, CO: Sounds True
2012
Pg. 112:
According to Benedictine monk Brother David Steindl-Rast, “It’s the silence between the notes that gives them meaning and grace.”