One of my favourite foursome/swinging experiences….
On a cushioned piano bench we put in the room for just this purpose my wife laid on her back on the bench and the other woman bent over her in a 69 position. I started fucking my wife and the other man started fucking his from behind. Everyone was so into as much back-and-forth as we could between wet pussy and wet mouth. I would fuck my wife with long deep strokes as the other woman bent over with her tongue stretched out to lick my wife's clit, and I would pull out and angle myself up just enough so she could take me in her mouth. I'd fuck her mouth while her husband pounded her from behind, her moans muffled by my cock.
Meanwhile my wife is reaching her head up to lick the underside of his cock as he thrusts deeply into his wife… he would pull out and fuck my wife's mouth, and then go back in his wife's pussy…her head is angled back over the back of the bench so she could deepthroat him well. I loved being able to run my hands along the other woman's back while she had me in her mouth; I could reach far enough to spread her ass while he fucked her… then I'd go back in my wife's pussy, and lean back a bit and use my hand on other woman's head to encourage her to lick my cock as I thrust in and out… this went on and on….so.fucking.hot.