The sound that is used in the UK version consists of one long blast of a chord played by brass instruments and the play the following musical notes:
- D Sharp which pitch bends to the following notes:
- G Sharp
- D (which goes down into a C Sharp).
The same sound was used in the USA until the shuffle format was introduced, in which the sound became a short blast of an air horn playing at note E.
Moments involving the KlaxonEdit
Contestants like Stephen Fox and Paul Cleary have been interrupted by the klaxon just after completing Fastest Finger. Contestants like Steve Devlin and Ingram Wilcox have been interrupted by the klaxon after winning £500,000 and had to wait until the next night to see the million pound question.
- Every time the end of an episode, unless a contestant walks away just before the end.
- On the UK electronic game if the player presses the pause button.
- Who Wants to Be a Millionaire? Party Edition on PS2 if the player runs out of time.
- Chris Tarrant normally reacts with "Oh, no!" when the klaxon sounds. On the 10th Anniversary Special though, there was no klaxon, as Regis just said that the contestant had to return the next night, before the celebrity came into the studio for their queston.
- The klaxon went off twice in the 2011 Mother's Day special. When it went off the first time Chris didn't hear it, so they sounded it again.
- Contestants have been interrupted by the klaxon after winning £500,000 and had to wait until the next night to see the million pound question. On even rarer occasions, some contestants have been interrupted by the klaxon just after completing Fastest Finger.
- The klaxon, unlike most musical scores, never appears in many of the Who Wants to Be a Millionaire? video games, but does in the electronic game when the game is paused.