John Dankworth CBE (1927 - 2010) was a British composer, saxophonist and clarinetist married to Cleo Laine his vocalist with the band.
'Dunsinane Blues' was written by Dankworth as part of a series of Shakespeare settings set to music by various composers and recorded by the band with Cleo Laine on vocals.
It describes how Macbeth thought he was immune from harm from Macduff as an apparition told him that he should 'never be afraid of death or bain 'til Burnham Forest came to Dunsinane and then only from a man that is not of a woman born'. But Macduff had a cunning plot!
Dankworth's discography can be found here.