In this series, Sir Antonio Pappano, Music Director of the Royal Opera House, examines the art and science behind the four major voice types: tenor, soprano, mezzo-soprano and bass-baritone. 　　He explores the vocal glories of the greatest stars to emerge since recording began - Caruso, Callas, Pavarotti, Sutherland, Nilsson, Chaliapin, Baker, Dietrich Fischer-Dieskau, Verrett and...