speakers are not digital,
anything you can play through speakers you can record on your tape deck, its just audio. despite all the "digital electronics" speakers are and always were analog
I have a tape deck from 1952, made in burmingham england. 12" reels, tape heads are about an inch tall inch in diameter. its the same size as a regular sized stove. 1/4" tape, the ones I got with it are acetate tape.
well the research got really interesting indeed, the company that made my deck. ( bradmatic in birmingham) it helped with the design and manufacture of the mellotron
the mellotron was not a synthesizer, it preceeded them and out of that came a lot of music that you will be familiar with hearing. strawberry fields, moddy blues a lot of bands used them and because digital and syntesizers took off well music was never quite the same..
it can be hard to recognise the sound of a mellotron because they keys are recordings, so it can sound a lot like any instrument you base the tapes upon.
in essence each key on the keyboard of a mellotron has its very own tape reel.
so what i have here is a giant deck which is actually a piece of music history.
if you are interested hers a page that explains more about this important history this can really send you down a rabbit hole of interesting facts and reading.. the resulting influence it had upon the music industry was huge.
https://everything.explained.today/Mellotron/#google_vignette
next question, what the heck should I do with this thing? ;-)