In the days when FM stations could have subcarriers at both 67 and 92 kHz on the baseband, Muzak would put its standard service on 67 and a more contemporary, upbeat service on 92. Some markets had just one, some had both - and of the ones with both, sometimes the 67 and 92 subcarriers were on different stations (this was the case in St. Louis).It was supposed to mask ambient noise, also. But the tone and content of the MUZAK material was designed to be a "buying atmosphere" that was friendly, positive and comfortable. Once MUZAK was able to do multiple channels, they created multiple channels targeting large retail, boutique retail, restaurants, service locations (auto repair, etc) and the like.
Seeburg also used subcarriers.