In 1963 The Kingsmen paid $25 to a guy with some recording equipment and a microphone. The microphone was suspended from the ceiling about the lead singers head. In that session they recorded the a cover to a calypso song Louie Louie. 

Shock, horror: the Kingsmen performing live, possibly singing Loui Louie.

Their rock cover was a mild hit with DJs and started getting airplay that is until a Sarasota Jr. High School teacher heard it. She thought she heard some obscene lyrics.

“The lyrics are so filthy that I can-not enclose them in this letter,’” she wrote “We all know there is obscene materials available for those who seek it,” then added “but when they start sneaking in this material in the guise of the latest teen age rock & roll hit record these morons have gone too far.”

So the FBI started an investigation to determine if the Kingsmen and their record label had broken a federal law of distributing obscene material over state lines. They sped the song up they slowed it down to see if they could make heads or tails of the words. Were they singing We gotta go? or touch down low? After a two year investigation they determined that the lyrics were unintelligible. The 119 page FBI report can be found here.
During the entire investigation they never asked Jack Ely the lead singer of the Kingsmen what he sang or listen to the original calypso version of the song where you can understand the words. The even failed to exonerate Jack Ely but he didn’t mind he thought the investigation was one of the reasons the song has been immortalized.