I think you're confusing Muzak™ with the radio formats known as "Beautiful Music" and "Easy Listening." Muzak™ is neither of those. Most musicians at the time Muzak™ was prolific actively refused to even call it music.
Muzak is basically a corporate slurry genre that was designed by psychologists to have calming, semi-hypnotic effects on listeners doing repetitive labor, trapped inside confined spaces like airplanes and elevators, stuck on hold, or wandering the isles of grocery stores. The company actually forbade its use outside psychological applications like that, as they apparently didn't want overexposure dulling its "psychological and physiological effects" on listeners in the intended environments.
That said, I can't imagine anyone back then ever
wanting to use it outside its intended scope -- like by programming a radio station with it. Unlike actual music (which, yes, includes Beautiful Music and Easy Listening), Muzak is designed to
avoid moving the spirit or creating mental excitement and engagement. It's basically crafted to "just lay there," like pastel patterned wallpaper for your ear canals.
Here's a sample of Muzak as packaged for Delta Airlines: