"TSOP (The Sound of Philadelphia)" is a 1974 hit recording by MFSB featuring vocals by The Three Degrees. A classic example of the Philadelphia soul genre, it was written by Gamble and Huff as the theme for the American musical television program Soul Train, which specialized in African American musical performers. The single was released on the Philadelphia International Records label. It was the first television theme song to reach number one on the Billboard Hot 100, and it is arguably the first disco song to reach that position. Background The song is essentially an instrumental piece, featuring a lush blend of string instruments and a horn section in the Philadelphia soul style. There are only two vocal parts: a passage close to the beginning during which The Three Degrees sing "People all over the world!"; and the chorus over the fade out, "Let's get it on/It's time to get down". The words "People all over the world!" are not heard in the original version. The version heard on Soul Train also had the series title sung over the first four notes of the melody, "Soul Train, Soul Train". This particular version was released on a 1975 Three Degrees album, International. "TSOP" hit number one on the U.S. Billboard Hot 100 in the spring of 1974 and remained there for two weeks, the first television theme song to do so in the history of that chart. It also topped the American Best Selling Soul Singles (for one week) and adult contemporary (for two weeks). The Three Degrees would revisit the top of the AC chart later in 1974 with their hit single, "When Will I See You Again". Don Cornelius, the creator and host of Soul Train, refused to allow any references to the name of the television series when the single was released, leading Gamble and Huff to adopt the alternate title for the release. Cornelius would later admit that not allowing the single to be named Soul Train was a major mistake on his part. (As a result, the Three Degrees' singing of the show's name "Soul Train" during the chorus as heard on the TV version is not heard on the single.) Although it was rerecorded a number of times for future versions of the show, and various different themes were used during the late 1970s and early 1980s, "TSOP" returned in the late 1980s and remained