A friend shared this Reverb link to a vintage 1984 Casio EG-5 from Japan, an electric guitar with a built-in speaker and built-in cassette player. The tape deck could be used to record loops of your own playing, or with pre-recorded accompaniment — and you could control the speed/pitch of the playback, too.
A few more details from the listing:
The onboard cassette player functions include Play, Rewind, Fast Forward, Stop/Eject, Pause, and most importantly Record. This gives the user the ability to play along with program material, or record their own licks directly to tape. A Tape Pitch dial offers the ability to change the speed of the machine on the fly. The built-in amp has a nice ripping, fuzzy push-button distortion and quite a bit of volume, offering a clean signal as well with the distortion disengaged. It's just plain fun!
The one-piece maple neck has a slender C shaped profile with modest shoulder and lightly rolled fretboard edges, measuring .805" deep at the 1st fret and .865" at the 12th. The maple fingerboard features black dot inlay and stock medium jumbo fretwire. The frets are virtually flawless, and the guitar plays cleanly up the fingerboard with a 12" radius. The scale length is 24", and the nut measures 1 5/8" in width. The headstock features the original Casio logo and set of chrome tuners that turn smoothly and work as they should.
On the body, all of the electronics function accordingly, with a Main Volume slider, Guitar Mix slider, Drive slider, Distortion On/Off button, and Master Volume knob next to the speaker. The cassette works with aforementioned controls, while the Tape Pitch dial, Power On/Of switch, DC 9v jack, Guitar Out, Phones out, and Line In jack are recessed on the treble side lower bout. The guitar is powered by a sextet of batteries located in the back or via an optional 9v power supply (not included).
What a weird but wonderful musical toy. And how very 80s casio.