As Mood Media retires its most famous brand name, Muzak, let's pause to recall that the operation was responsible for more than just the sonic custard that people associate with the Muzak label. Theodore "Arwulf" Grenier, host of an excellent jazz show on WCBN-FM, points out that
Muzak was one of many transcription services for which musicians—many of them now regarded as legendary jazz artists—regularly cut recordings that weren't peddled to the public in stores. The only time anyone heard these sides (which often exceeded the 3.5 minute limitations of the ten inch 78 rpm record) was when they were aired over radio waves as filler. Transcription recordings by Duke Ellington, Claude Thornhill and dozens more have been reissued and often represent some of the best material we have from that period (30s & 40s). I believe this was largely due to the fact that the A&R directors usually associated with commercial recording sessions were absent or "defanged" for the transcription sessions, which weren't geared towards selling units in stores.
That's right: The company that has probably received more sneers from music lovers than any other corporation not only recorded some of the greatest jazz artists of the last century, it often gave them more time and freedom than the major labels did. Arwulf goes on to describe Fats Waller's Muzak sessions, "which underline perhaps the most important and least recognized aspect of Thomas Waller—his subtlety." There's a link to one of Waller's Muzak recordings too. Read the whole thing.
Bonus link: In recent years, Muzak moved away from elevator music and into elaborate experiments with niche-targeted "audio architecture." David Owen describes the results here.