8-track
the cassettes this thread is about are 4 track btw. that's 2 stereo tracks running in opposite directions. that's why sometimes when the tape would get fuct up, or the player was bad, you could hear the other side of the tape playing backwards
the old 4-track multitrack recorders would use all four tracks going in the same direction. then the volume, pan, and bass/mid/highs, for those tracks could be adjusted and mixed down to a stereo mix. it also allowed for overdubbing, where your could record one track, and then play it back while recording another track. this was a valuable tool for early hip-hop (and other genres)
8-tracks were basically more complicated and suffered because of that. 8-track players were pretty much exclusive to cars. you could buy home players, but vinyl was still the go to format at home. you couldn't record on 8-tracks, so that created the issue where you would have to pick a format, or double dip. they had 4 stereo tracks going in a continuous loop. that meant you couldn't rewind, but you could switch between the four tracks on the fly. that generally complicated things though, because again vinyl was still the standard, and that was a stereo track split onto two sides of a record. sometimes they would have to rearrange the song order to get that to fit right on 4 stereo tracks. plus the mechanism was more complicated and subject to jamming. and four stereo tracks increased the chance of the playback head picking up some of the wrong track
all of that led to the 8-track having a rather short run. "compact cassettes" (what this thread is about) were around before and after the 8-track. it just took a lot of advances in their sound quality to get them to the point where they could be used for commercial music. plus you could record and rewind, and the two-side format easily mimicked vinyl. I vaguely remember in the early 80's most popular music came on all 3 formats, and some people had monstrosities like this: