Rick wrote:
I've seen that in some movies from the '40's, so I guess it was a real deal.  Some sort of combo radio/jukebox/telephone operator.  I don't think the operators usually sang along with the records, though.  Must be something on this phenomenon somewhere on this worldwide web thingy.
This poorly-worded sentence is all that I've come up with so far:

During World War II, Rock-Ola led the industry with the introduction of telephone-line music transmission systems, which proved very successful because it kept the jukebox going at a time when non-essential manufacture was severely restricted because of wartime rationing, and the record industry was hit hard by the scarcity of shellac, which was obtained from South East Asia.