The singing prostitute

A guy is sitting in a bar finishing his beer when a prostitute comes over.

"Hey honey, for fifty bucks I'm a blow you and sing the national anthem while I do, waddya say ?"

The man replies "The humming will sure be quite the trick, here's your cash !"

The girl gets him into a small appartment just outside the bar. She leads him into a room, sits him on a chair then shut the light off.

While getting the head of is life in the dark, he hears singing "Oh say can you see..."

Suspecting something weird going on since she clearly sings with a mouthful, he reaches for his trouser pocket on the floor where he got a small flashlight on his keyring.

Swinging the light around he stops the beam on a sidetable where he spots a glasseye...