tape stop is a literal reference to stopping old school tape players and turntables that wouldn't completely halt when stop was hit and would take a moment, which would play the audio as the tape decelerates to 0 rpm. the easiest way to recreate this effect is to resample the section of your track that you want the tape stop to happen at - make sure it's the entire track - then throw it into a sampler and modulate the pitch. You'll need a huge pitch adjustment - 6 or more octaves, so you might have to play the "note" say 4 octaves lower than it is supposed to but have your pitch envelope start at +48 and finish at -48, depending on what you're using.
the most important thing is resampling the entire track because you want every single element diving at the same rate, including reverb and post processing effects. If you have a reverb that sits on top of your master for wideness and this doesn't get included in the tape stop it won't have that abrupt stopping effect. You don't have to worry too much about waiting for a master or final mix down as long as the elements are close to the final product. They will be so distorted it won't be noticeable anyway, and going from a wide final track to a tiny section that doesn't have mastering effects or stereo enhancement during the tape stop will only exaggerate the effect.
Also - you can put a utility on it (if you're in ableton) or any other effect that allows you to filter out all stereo frequencies and have it go from 100% (stereo field the way you intend it to sound) to 0% (mono only), which will create a shrinking effect that will let whatever comes after the tape stop really explode across the aural spectrum. You could put this same effect on your master and have it go from 0%-100% in 1/16th or 1/32nd so it sounds like your track is exploding out of whatever it stopped into.
