Two different associations come to mind about this portfolio title, both of which hit the core in different ways:
Gregorian chorales and Zen koan "The Sound of the One Hand Clapping."

Gregorian chorales are characterized by a simple melody line and a free rhythm that adapts to the text. The melodies are mostly modal and use a limited number of notes, resulting in a meditative and spiritual sound. So are these photographs: simple forms, few colors, but full of concentrated energy. And by meandering in a few colors, a powerful dynamic is created.
The famous Zen Koan by Hakuin Zenji reads:
"You all know the clapping sound of two hands, but what is the sound of one hand ?"
Zen koans are puzzles that can only be solved intuitively, not by any amount of thought or brooding. There is a non-verbal answer in some of these photographs.