Despite having written two of the most enduring modern musicals – Cabaret and Chicago – composer John Kander and lyricist Fred Ebb routinely had numerous new shows on the go that struggled to reach completion or production. This was largely because the song-and-dance form is the hardest type of theatre to get right, due to the number of different elements involved and the inherent artificiality of speakers bursting into song. When Ebb died, in 2004, the unrealised pieces might have been assumed to have gone with him. But, in a touching tribute to his life-long collaborator, Kander has completed  first Curtains (2007), a showbiz murder mystery that was a Broadway hit and deserves a major British production, and then The Scottsboro Boys (2010), which has opened at the Young