] Each musical subscriber is supplied with a special
] directory giving names and numbers of records, and the
] call number of the music department. When it is desired
] to entertain a party of friends, the user calls the music
] department and requests that a certain number be played.
] He releases and proceeds to fix the megaphone in
] position. At the same time the music operator plugs up a
] free phonograph to his line, slips on the record and
] starts the machine. At the conclusion of the piece the
] connection is pulled down, unless more performances have
] been requested.

Turn of the century online music on demand.

Distributing Music Over Telephone Lines (1909)