Background: There is a cassette recorder (RadioShack CTR-80A) and its owner would like to have the ability to speed up and slow down the motor to record and play the sound in a distorted way. We've done a similar thing already to a Sanyo TRC-3460 voice recorder, but its diagram was easier to understand.
Question: Where in the following diagram one would put a potentiometer to achieve a distorted effect (slow down or speed up a bit) when recording or playing audio from a cassette? What value should that potentiometer have?
Also, could you please point me to the resource describing the symbols which are used for switches in this diagram (the ones with white and black triangles). I've search high and low and do not understand what they mean. Well, not well enough, anyway.