[PD] reverse & variable speed soundplayback?

hi all to gain some understanding of this wonderful & mysterious world called pd, i'm building a little sampler / soundfile manager to use with my hardware roland spd-s (midi drumcontroller). it's all going well and it's fun trying to get my mind around all the semi-maths involved, but one thing i just don't know where to start with is how to play the sound back in variable speeds (preferably controlled by a number box) and / or backwards. in the helpfile for [play~] it says it does it, but i find its workings rather unpredictable... i'm now using [tabplay~] in my abstraction, mainly because of the [bang] it outputs after finishing (so i can make it loop) and because it plays back immediately. thanks a lot, robbert