Keith Semple took part in the ITV television series Popstars: The Rivals, a British singing competition.

• Week 1, he sang "Reach Out I'll Be There" from The Four Tops. He was safe.
• Week 3, he sang "Over My Shoulder" from Mike + The Mechanics. He was safe.
• Week 5, he sang "Sorry Seems To Be The Hardest Word" from Elton John and Bernie Taupin. He was safe.
• Week 7, in the boys' final, he sang "You Are So Beautiful" from Joe Cocker.

Host Davina McCall announced the names of the five contestants who had qualified for the boy band. Keith Semple was the first member to be announced followed by Matt Johnson. Third was Daniel Pearce and fourth Anton Gordon. The last available place went to Jamie Shaw whereas Chris Park was eliminated from the boys competition.

Semple and the four other contestant winners (Anton Gordon, Matthew Johnson, Daniel Pearce and Jamie Shaw) went on to form the group One True Voice.

The same show had also produced the girl group Girls Aloud also won the competition.

Keith Semple became a band member of the boyband One True Voice created as a results of the competition. The line up of the band was decided by public vote, who voted for their favourite male hopefuls each week to form the boyband. The name of the band was later shortened to OTV.

One True Voice was made up of:

• Anton Gordon (from London, England)
• Matt Johnson (from Deeside, Wales)
• Daniel Pearce (from Kent, England)
• Keith Semple (from Larne, Northern Ireland)
• Jamie Shaw (from Cardiff, Wales)

Their debut single, a double A side hit single "Sacred Trust/After You're Gone" went head-to-head with Girls Aloud on 16 December 2002, for the Christmas number one spot. One True Voice lost out to the girls and had to settle for the UK Christmas No. 2 position. The group's manager, Pete Waterman, has speculated that the show was fixed against OTV, but has not said how.. In any case, the single "Sacred Trust/After You're Gone" reached gold record status.

One more Top 10 hit followed, in the form of "Shakespeare's (Way With) Words", which reached No. 10 in the UK, in June 2003. A few weeks later it was announced that Daniel Pearce, who as arranger and co-writer of some of their songs had quit the group to pursue a solo career. The next day the group disbanded.

The group appeared at number 32 in Chantelle's Top 50 Reality TV Stars, ahead of both Phixx and Clea who also appeared in Popstars: The Rivals.

After the split Keith Semple continued his musical career reforming his pre-OTV band, the Keith Semple Band, then fronted the band Alibi.

In 2008, Keith Semple moved to the United States and joined Chicago-based rock band named 7th Heaven as their lead singer. This resulted in a critically acclaimed album USA-UK alluding to the co-operation of this UK act in an American band.

During Keith Semple's membership, the band consisted of members:

• Keith Semple – Guitars, Vocals (lead singer), Keyboards
• Richard Hofherr – Guitars, Vocals, Keyboards
• Mike Mooshey – Drums
• Mark Kennetz – Bass, Vocals
• Nick Cox – Guitar, Vocals
• Tamara Mooshey- Vocals

With Semple the band released a number of studio and live albums: Medley CD (2007), U.S.A - U.K. (2008), Unplugged (2009), Pop Medley 2 (2009), Medley CD/DVD (2010), Jukebox (2010), Merry Christmas in Chicago (2010) and Pop Media (2011). He left the band in 2012.

In 2012, Keith Semple left the band and was replaced by Anthony Fedorov, a contestant finalist on the fourth season of American Idol.

In January 2010, Keith Semple successfully auditioned for the ninth season of American Idol. He was put in the intro to the Chicago episode of the American Idol.

Keith Semple says Simon Cowell was reportedly "unhappy" he did not tell his band members 7th Heaven in advance about his audition. But Fox Chicago affiliate offered to film Semple telling his band 7th Heaven and allowed them to perform together on Fox, thus giving him a fres