We'd probably have records with twenty parallel grooves and reading heads with 40 or more needles.
I'm an old fart. I worked on a Burroughs B3500 back in the 70s. The "Disk Module" was a 10MB cabinet about 4 ft by 4ft by 2ft. It had 4 platters and there was one head per track. Seek time was non-existent but rotational delay was a bitch.