The harness is in fact your parachute harness. When the seat deems it safe for separation a few things happen pretty much at the same time: the scissor shackle opens allowing the drogue to pull out the main chute, also the should retraction parts of the harness are released (clockwork type mech I think, part of the baro time release unit) and the negative g strap is released (similar mech to above and is a strap from the QRF to the seat betwixt your legs (don't know if that's a word). The final 2 places you're held into the seat normally are the leg straps and these are fixed to the seat in spring loaded sticker connections - a good, sharp tug (like what occurs when the main chute opens and rapidly decelerates brave unfortunate Biggles) pulls these out. Thus all that remains to be seen is that the bottom of your parachute meets the top of your harness.......