Pinkie Pie and Fluttershy were having consensual sex in the missionary position.
The stereo managed to drown out their cries as it blared metal across the neighbourhood, the kick and snare pounding off like a machine gun. If you listened closely you could just make out the lyrics:
I smoke lots of crack and my girlfriend has a kid!
I like drugs and child abuse!
When she’s in the bathroom, I kick him in the balls!
I like drugs and child abuse!
When she’s at work, I teach him how to shoot up!
I like drugs and child abuse!
When she beats him up, I sit there and laugh!
I like drugs and child abuse!
Angel cowered behind a chair, unable to not see the horrible spectacle.
They switched positions, to the Amish Plow, to the Alabama Hot Pocket, to the 72. Pinkie Pie got kneed in the eye, Fluttershy farted and queefed, Pinkie threw up into Fluttershy's vagina.
The mood changed slightly as a new song came on. This had no discernible lyrics whatsoever, and featured a fart piano in the harmony. Now they grinded against each other, dripping with fluid and barf, making screams on frequencies reserved for fangirls and dog whistles.
Eventually, after a few new positions and 'songs', the two ponies became aware of a low-quality unearthly thumping and coarse shrieks that were NOT coming from the stereo. They were coming from outside.
At about that moment, Pinkie's phone buzzed with a message from Twilight Sparkle: "Celestia wants us to report to Canterlot immediately"