Originally Posted by kbarnes701
I'd add that the recently deceased Ray Dolby's contribution to the cassette medium was also one of the milestones in history which helped the transition of cassette from 'office use' to a viable medium for listening to music.
His success with cassette was preceded by his very helpful noise reduction for studio tape recorders - Dolby A.
Dolby A was a somewhat fiddley multiband system. It was highly dependent on reference levels being just right.
Dolby B was essentially a single band system, but the corner frequency moved down at low levels. The hidden agenda was that Dolby B was also dependent on level matching and was not a truly reciprocal system. IOW the decode phase was not the perfect mirror image of the encode at its best and if the playback level was off, the decoding was even less of a reciprocal and the playback was colored.
All analog tape systems have limited dynamic range at higher frequencies and also compress dynamics pretty heavily. The slower the tape speed, the greater the compression and the lower frequency at which it starts.
With the best modern tapes and tape machines, wide tape and tracks, and 15 ips operation, tape compression is pretty mild in the audio band. When you are talking the tiny tracks on cassette machines and the snail's pace of the tape, the compression starts around a few KHz.
The other audible artifacts of analog tape include flutter and wow (now known as jitter), fringing effects at low frequencies, and drop outs. Many of these slide by unless you can do a direct instant-switched time-synched comparison.
I admit it, I like to torment analog tape bigots by pointing out that the best analog tape machine ever made had jitter that is about 1,000 times more than the worst real world modern digital. But, its true. Good thing that jitter is not all that audible! ;-)
BTW that tape-induced jitter is part of every digital recording that started out with analog tracks. Analog systems were heavily developed over the years and while many of their shortcomings were inherent and had to be there, they pushed into frequency ranges where they were less audible.