Although many of the writers hired did write original compositions, most of Muzak was familiar popular and Light Classical melodies arranged for salon ensembles and dance bands, including current pops."But Muzak, as we came to know it, was never planned as listening music. Though much of it was quite listenable even when presented in the sonically flattened manner they used. Or so I thought."
Early Muzak were original compositions arranged to fit the Stimulus Progression architecture.
Later, the sound/library was revamped to present pop cover of hits by Jack Kent Cooke who owned the company at the time making it more "listenable." This began the era where supermarket cashiers could tell you how many versions of the song "XXX" they had heard being played.
I found an interesting blog about it here: Muzak Refresh
What they called "Stimulus Progression" was not copyrighted until 1960, but was used at least since after World War 2. Based upon what had been done in England with Music While You Work but more refined. To help get workers through mid-morning and mid-afternoon slumps. Later they took their recordings and assigned numerical values based upon the number of musicians, the orchestration, tempos, style, etc. and arranged music segments so with each selection the assigned values increased. That basically was their "science". Hardly anything earth-shaking but they did employ many good arrangers who wrote some decent and enjoyable arrangements.
