When a chick gives a guy a reach-around while pressing her lips to the asscrack of a guy as he farts, thus making it seem and sound like she is playing a rusty trombone. Makes me want to join the marching band.
The act of performing anal cunnilingus while reaching up above the testicles to manually administer quick up and down motions to the penile shaft; resulting in a violent yet pleasant explosion. It is then customary for the female to then give a quick blow into the anus for good luck, the lips blowing into the anus sounds very similar to a trombones sweet melody. This was introduced to the Americas in the late 50's.
While receiving a rusty trombone I lost control of my bowels.