A man see a sign in the window on his way to work, "Singing Blow Job - $25".
He spends the whole day curious about it and decides that $25 dollars isn't that much to slate his curiosity.
He goes in the building, pays the money, and is lead into a small room. Inside the room is just a chair and a table. The only thing on the table is a glass of water. Once he sits down in the chair, the lights go off. He hears somebody enter the room and the singing starts.
It's a beautiful operatic voice that seems to ebb and flow with the movements of the blow job. The song comes to a great climax, in sync with his own.
Now, even more curious the man decides to go back again, but this time he smuggles in a flash light. He enters the room again and has a good look around, confirming that there are no speakers, radio, or audio equipment that he recognises. He sits down and waits for it to start again. Once the blow job starts, he turns on the flashlight.
There is no one else here. Just the woman in front of him, her head bobbing up and down. The music truly seems to be coming for her. Confused, he drops the flashlight on the table.
That's when he sees it. Floating in the glass of water.
A glass eyeball.