McCarthy trained as a baritone singer at the Guildhall School of Music and Drama and the London Opera Centre.
[1] On 7 August 1974, McCarthy was in attendance at The Proms performance of Carl Orff's Carmina Burana, performed by the London Symphony Orchestra and conducted by André Previn in the Royal Albert Hall.
McCarthy went backstage and offered his services as a professional singer who was experienced with the piece.
The understudy for the part, a member of the London Symphony Chorus, was a doctor and attended to Allen, and thus was unable to step into the performance.
[5] His voice had changed and he became a tenor singer, before moving to orchestral and choral conducting in 1992.