It's going down: a lawsuit has been filed over Pitbull/Kesha's #1 smash, 'Timber.'

Three songwriters have filed a law suit in Manhattan Federal Court, claiming that 'Timber' rips off their 1978 song 'San Francisco Bay.' The writers say they're owed money from the record label for copyright infringement. Neither Pitbull nor Kesha are named in the suit.

Among the plaintiffs is harmonica player Lee Oskar. According to the paper, the suit alleges that Paul Harrington, who played harmonica on 'Timber,' was told to "emulate" Oskar's harmonica part in "San Francisco Bay" so it would have "an identical texture and sound."

The suit further alleges that even if the record company, Sony, obtained a license to use the song, they didn't get it from the songwriters, who haven't made any money from the hit song. The trio -- which, in addition to Lee Oskar, includes Keri Oskar and Greg Errico, according to Wikipedia - is seeking $3 million in damages. Seems reasonable considering how much money that song has made! Here's the song in question:

And, here's an instrumental of 'Timber' to compare: