"Seeburg, the jukebox maker, produced a background music system called, strangely enough, the Background Music System. It used 16-2/3 RPM 9" records with 2" center holes. They look like big 45s. These machines were used to play elevator music in the 60s and 70s. The player was the size of a microwave oven and played up to 28 records in a stack, for 40 hours of music. It automatically restarted the stack for continuous music. The records were issued and owned by Seeburg Music Library Inc. and manufactured by RCA Custom Records. The instructions on the record boxes say they were to be played for 3 months then returned to Seeburg to be destroyed. That's probably why the records are so rare. Also, these machines were all mono because that's how public address systems were wired. " (description from David Forbes, david@ioinc.tucson.az.us)