Of course, a true artist can adjust the pressure of the flow to go all the way from a faint rumble to a full-crescendo sonic blast. They will also vary the the resistance level between said buttcheecks and furniture to vary the pitch as well. I had a friend in college who thought farts were the funniest thing in the world. I would say he was (sadly) a virtuoso.
(Okay, if you really stop to think about it, farts are funny. I mean, anybody seen Blazing Saddles??)
"More beans, Mr Taggart?"
"I'd say you've had enough!