I think it's clear that, being a classical saxophone performance-- even at the world saxophone congress-- they just couldn't sell enough tickets to keep the lights on...
Rosco #74, 385, or 181 gels are not that expensive. Onstage 'shadows' are not done with 'dark'--they're done with blue light. Lighting design 101, 2nd week of class.
Shadows are not the absence of light. They're just lower albedo.
Sound guy theory of relativity: E=mc^2 (+or- 3dB)
Sax player theory of relativity: E=mc^2 (+or- .010" at the tip)
"Free jazz is the vegemite of the musical world. It's an acquired taste."-J. Jacques