Finalists Lee Mead, Lewis Bradley and Keith Jack have each already recorded the number, "Any Dream Will Do".
All three will feature on the other track of the double A-side single, which is the exit number "Close Every Door".
The proceeds of sales will go to the BBC's Children in Need campaign, according to Andrew Lloyd Webber's Really Useful Group.
The single will be available to download from 12 June and in shops from 19 June.
The winner of Saturday's final, to be screened on BBC1, will star as Joseph in London at the Adelphi Theatre, Joseph and the Amazing Technicolor Dreamcoat, next month.
Lord Lloyd-Webber said: "We have an intriguing contest.
"I wouldn't like to second guess who is going to win in the end."
For more information, go to www.josephthemusical.com.
