This reminds me of a time when my wife actually made one of my 'taboo fantasies' come true. For a while, my wife and I exclusively met with only female SP's. I then got the itch to watch her with other men. Although I have now seen her with a few over the past couple of years, the first ever experience of my wife with another dude was something similar to this post.
Before I actually sat in the same room while she was with another guy, she first had a couple of experiences without me there with my full approval (this was years ago). She would fuck the guy and then come home and tell me about it, detail by detail, and we would end up having mind blowing sex. Then, before one of her 'dates', I asked her if she could call me during the proceedings because I wanted to listen to her getting fucked. She said she would if the guy didn't get to weirded out by it. A while after she left, my phone rang and she told me that she wanted me to hear everything. It was fuckin incredible. She was narrating what was happening. She said things like 'he's sucking my nipples and getting them hard' and she would be softly moaning. She would then say 'he's now licking my pussy while he puts two fingers inside me'. The turn on that I felt was like nothing I ever felt before. I was rock hard and actually began playing with myself during this. I still remember vividly when she said 'he's now sliding his big hard cock inside me' and I was listening to her moaning and his grunts as they fucked. She was yelling out how she was gonna cum and how good it felt. I couldn't help it and just began jerking off on the other end of the phone. I heard him say that he was going to cum and then my wife telling him to cum on her breasts. I came at the same time as the other guy did.
That experience still stands out as one of the hottest things my wife and I have ever done, and I wasn't even physically there, which, for some reason, seemed so much hotter.
Picturing what she was doing while listening to her seemed to bring it to a whole other level.
It was definitely a fantasy come true, and I guess taboo as not every guy would probably get off listening to his wife getting fucked over the phone.