Music suddenly stops, deck starts going back and forth, and then the cassette is ejected in disgust, you insert it back and listen a sound of a motor spinning uselessly, that's the sound of a drive belt failure.

this can also happen to the cd receive and ejecting mechanism, cd will get stuck inside

Some of you might ask, who the hell still uses cassette decks ?! well.... me like most people have retrofitted an aux cable to their OEM headunit or using Cassette tape adaptor, for preserving the look and some functionality which otherwise can't be obtained from aftermarket headunit .

The real questions is ,,,DAMN !, where the hell am gonna find one today ?! we have to make it !

Step 1: Making a Replacement

i've looked for something that could be made to length with out having an obvious joint that hinders the mechanism's movement, embroidery floss or stranded cotton seemed logical, which can easily be obtained.

When removing the mechanism, remember to take note of how to belt is guided in the mechanism, if its not possible the original can be guessed by trial and error using the original belt, OR google is your friend.
The belt is removed from the mechanism and the mechanism is cleaned with a soft brush. this would be the perfect time to inspect them, to see if the belt failed because of normal use or something went wrong.
Couple of strands of cotton are rough cut longer than the neoprene belt.
The cut strand the is guided along the mechanism's pulleys
A single knot is tied to insure that the thread wont come of.
The knot is then moved to the smallest pulley on the mechanism, why? because the knot there wont slip and can then one can tie another knot without the first one getting loose

i've found that one knot will unravel obviously, two MIGHT unravel, three create a big lump but makes a strong knot, four is huge and unnecessary.

Step 2: Improving the Replacement

The excesses thread is cut with a pair of scissors as close as possible to the knot.

*if there is a little slack in the belt, the next step will remove it

The made belts are then bunched together and twisted to make a strong singe one.
The belt is covered with tire repair cement, because it strengthens it, and reduces slipping (increase its friction), it can be found in a tube or can, also in cheap tire repair kits (silicone sealant could work but takes long to dry)