"Girl You Know It's True" is a song that became the first big hit for Milli Vanilli. Released as the lead single from Milli Vanilli's European debut album, All or Nothing, and the duo's American debut album, Girl You Know It's True, the song peaked at number one on the German Singles Chart, number two in the United States and number three in the United Kingdom, becoming one of Milli Vanilli's most successful singles. This song is best known for exposing the lip-syncing of Rob Pilatus and Fab Morvan who were recruited after Frank Farian had completed production of the song.

The song was written by Bill Pettaway Jr., Sean "DJ Spen" Spencer, Kevin Lyles, Rodney "Kool Rod" Holloman (often misspelled "Hollaman" on single/album credits), and Ky Adeyemo, most of whom were members of the Baltimore, Maryland-based group, Numarx, who first recorded the tune.

Started by DJ Spen and featuring Kool Rod as MC, Numarx was a collective of local DJs who formed a "crew" in the early 1980s, originally consisting of four members. With the addition of Lyles in the mid-1980s, the group expanded to five. In 1987, with several singles under their belt, Numarx released the single, "Rhymes So Def," which received national airplay at the time. The follow-up single to this minor hit was "Girl You Know It's True."

The idea for the song began when Marvin Ennis suggested that the group (Numarx) rap about something romantic in Bill Pettaway's basement in Annapolis, Maryland. Bill Pettaway, an Annapolis resident working as a gas station attendant at the time also wrote songs and played guitar on the side. Pettaway, along with Numarx members Spencer, Lyles, and Holloman continued to craft the tune. In addition, then-current Starpoint member Kayode "Ky" Adeyemo joined in, co-writing and co-producing the song with Pettaway. However, the vocalist most prominent on this song is Charles "Ooh Oh Ooh" Christopher. Charles was friends with Pettaway, Adeyemo, Marvin Ennis, and George Philips (the latter three all associated with the former Elektra Records group Starpoint) and became the voice that everyone was singing along with. Although the song did not match the success of "Rhymes So Def" in America, "Girl You Know It's True" did connect with audiences on the other side of the Atlantic, becoming a popular hit in the German clubs. It was here that Milli Vanilli producer Frank Farian likely first heard the tune.

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Wikipedia