Christopher Hampton, who wrote Sunset Boulevard (ALW) and The Trial (PG), gives an icy shaft of insight:
‘With Lloyd-Webber you are given the music and and have to fit the lyrics to the score. Philip Glass writes not a note until he has the libretto, and then he will call if he wants to make a cut or needs a couple more syllables. He is the perfect collaborator because he makes every effort to honour the text and make sure every word is heard.’
Full interview here.