Okay, I read Unca Cece’s blurb on the subject:

But how did they used to deliver the broadcast?

Around the corner from where I live there is a convenience mini-mart with a little satellite dish with Muzak stenciled on it.

Today, Everybody and his sister has access to the Internet and/or satellite dishes to recieve broadcast, but what did they have in, say, the 70s?

Delivered by a dedicated co-axial cable or telephone line?

There is a lot of information on the origin, development and distribution of Muzak in Wikipedia.

As far as I was aware of Muzak in the 70’s, I was under the impression that the store or building used tapes with their in-house sound system to deliver music. I see that to some extent radio was also used.

I was surprised to learn Musak has been around since the 1930’s though. I would have thought it a much later phenomenon.

I’ve read that Muzak was (is?) distributed on FM radio stations using portions of the band each station does not need to use for their main programming, some kind of sub-band that is. The stations charged users for some kind of special receiver to hear the special signal.

That is right, called SCA for sub carrier authorization, I used to make adapters to hear what was on this band. Several FM stations had not Muzak, but their own “business music” to compete.

Then someone found more money in using the SCA to deliver commodity futures quotes which sounded like a 300 baud modem but was scrambled.

There was also a doctors bribery service called Physicians Radio News, it told doctors about new drugs to prescribe, and offered TV sets, free CD’s and even some free vacations for writing enough prescriptions so I listened to that one more than Musak. Another thing was some PBS stations had reading service for the blind and would read novels and such so much each day.

By the way this SCA sounded poor, you could always hear some interference from the main FM channel, one reason it was always played at a low level. Musak later moved to little sat dishes, and then last I heard it went under as it just was not needed anymore. A DVD full of business music could last all day now.

The FM specification authorizes a baseband bandwidth of 99 kilohertz, but a stereo signal only requires 53 kilohertz of baseband bandwidth (and a mono signal only 20 kilohertz). The FCC allows an FM licensee to use the remaining baseband bandwidth of the signal for nearly anything it wants, provided only that it meets certain technical limitations (found in 47 CFR §73.319). Examples of things that have been placed on subcarriers include “functional music, specialized foreign language programs, radio reading services, utility load management, market and financial data and news, paging and calling, traffic control signal switching, bilingual television audio, and point to point or multipoint messages” (§73.295).

There’s enough room for several voice-quality audio channels or one nearly-music-quality channel in there, but in practice the modulation limits in the regulations create problems.

I’d be curious to what extent SCA is being used today. I imagine it’s not much.