I recently bought a batch of early stereo reel to reel tapes. Stereo debuted on reel tapes, as you may know, about two years before the technology was adapted to vinyl records, and most of these tapes were dated 1956 to 1958.
In one of the tape boxes were several advertisements and business reply cards, and I was fascinated by the one for which I've included to the left, and which I've attached as a jpg, below. This sounds a lot like Karaoke, long before the term was ever heard. If you had a reel machine which had "monaural record and stereo playback" capability, these tapes made it possible for you to "add the melody" while the tape played the accompaniment.
The tape was reusable any number of times, and contained the types of songs which Mitch Miller would use to attain great fame doing more or less the same thing, albeit via television, a few years later. And all this could be yours for just $11.95, just about $90.00 in today's dollars. A bargain!