Still with Karl Russell, the group's first big break came in 1972, when they were invited to appear in the blaxploitation film, "Blacula", starring William Marshall. They were also asked to record three songs for the film's soundtrack: "There He Is Again", "What The World Knows," and "I'm Gonna Catch You." After their participation in the "Blacula"-project Karl Russell was replaced by Fleming Williams and the group signed with RCA Records; their second single for the label, "Freedom For The Stallion", from the album of the same name, became a moderate hit, reaching #63 on the "Billboard" Hot 100 chart. The third single from the album, "Rock the Boat," became a #1 hit on the "Billboard" chart and the group's signature song. The bass player on the session for "Rock the Boat" was Wilton Felder, not James Jamerson as previously reported. "Rock the Boat" was written by Holmes, who also wrote the Blacula songs, and was released in the U.S. in February 1974 and in the UK in July of that year. It went to #1 for one week in the U.S. and #6 for two weeks in the UK, staying for 18 weeks in the U.S. chart with a gold disc awarded by the RIAA on 24 June 1974. The track sold well over two million copies. The song is considered one of the earliest disco songs. Some authorities proclaim it to be the first disco song to hit #1, while others give that distinction to "Love's Theme" by the Love Unlimited Orchestra, a chart-topper from earlier in 1974.