I copied all of these instructions from my friends flickr page who was so gracious to share. I'm not really sure I understand whats going on here but wanted to copy it for this community, and also to practive this whole 'instructable' thing. There are several techniques that people used to manipulate cassette tapes, and I hope to document many of them.
"I'm not sure if anyone has ever documented this before, but this set is devoted to what I'm calling "tape surgery", for lack of a better term. All you need is an old cassette that you don't care about and somewhere to play it. (I don't have a working tape player any more so I can't verify if this actually works the way I remember it.) What you end up with is a make-shift mashup tool -- no fancy software or high-end recording equipment required. Interested? Read on... "
Step 1: Tape Surgery
Step 2: Tape Surgery
Step 3: Tape Surgery
Step 4: Tape Surgery
Step 5: Tape Surgery
Step 6: Tape Surgery
"With the surgery complete, use your finger to wind the tape back up. "
Step 7: Tape Surgery
Hex wraps it up...
"You can't tell from the picture, but the magnetic tape itself is now upside down. If you rewind it (or maybe fast forward it... I can't remember) you can start to mess around with recording and playback. Whatever was originally recorded on the tape will sound through, albeit faintly, in the background with your new recording overdubbed. The recording may take on other bizarre properties -- mangled, backwards, slowed down, etc. I don't really know what is actually happening or why, but I remember doing this a lot when I was a kid. Perhaps this is where my obsession with experimental audio began, or maybe I just liked to break things. Anyways, let me know if you have any success with this technique. "