As part of the BBC Talent scheme they are looking for two "energetic singers aged seven to 16" for the lead parts, and 25 to 30 kids to join the chorus.
Blue Peter will follow the progress of the young singers, who should never have sung on TV before.
The show will go out at Christmas 2004. Details are at www.bbc.co.uk/talent.
Auditions are being held at Cardiff, Belfast, Glasgow, Manchester, Birmingham and London.
If you're interested, the deadline for entries is 31 March 2004.
People will be randomly chosen from the entrants, and there will also be a first-come, first-served audition in each city.