The MT8x records using the entire width of the cassette tape onto eight tracks.
A regular cassette deck records in stereo using both directions of the tape, so there are four physical tracks.
The tape heads on the regular deck can only play a tape confiugyred this way. The tracks on your tape are half the size and four of them will be backwards relative to what the normal tape heads are trying to play. I expect you get no sound because the tracks are too narrow to cause the head to respond very well at all.
You are supposed to mix the eight track tape to a stereo master to get something you can play on consumer equipment -- a stereo cassette dack or a stereo audio CD or watever form.
Depends on if you want one in a computer (a CD-R/RW drive) or a stand-alone external unit like another piece of home stereo equipment.
If it's the former, I have always had great success with Plextor products. (And keep in mind, you need to get the mix onto the computer before you can burn it to a CD.)