Bernstein, probably best known for his musical West Side Story and his score for the film On the Waterfront, received honorary membership of the school when the Mass was performed.
At the time he said: 'I came into rehearsal for my Mass intending to stay for 15 minutes and I stayed for four hours, I was so impressed and moved. I have been in and out of the school ever since.'
Although Bernstein left scores to American colleges, the Guildhall is thought to be the only English institution to have been honoured.
'The Mass is one of the events people still talk about,' said Ian Horsbrugh, school principal. 'Although he didn't conduct it, he came to the performance and has always maintained an affinity with the school ever since.
'Composers will be able to study his instrumentation and pick up all kinds of things about the way a score is written.
'As far as I am aware scores have been left to four or five music colleges around the world. These are the only ones to come to Britain; most went to institutions in the States, so it is a great honour for us.
'They are all significant works from a major figure of the 20th century. For people doing research on Bernstein it something they can turn to. Access to the scores, to be kept in the library, will be restricted to Guildhall students and researchers.
Mass interwove Latin with popular peace songs in English, in an attempt to re-evaluate the old text with contemporary
It was created at the suggestion of Jacqueline Kennedy Onassis and first performed at the opening of the John F Kennedy Center in Washington in 1971. The programme on the Guildhall performance stated: 'It is useful to recall that the work was conceived against the background of American
society emerging from the
horrors of the Vietnam War and the traumas of the civil rights campaign. The climax is a gigantic and raucous cry for peace.'
The Guildhall Mass was described as a fusion of
rock opera and jazz with
interludes of Shostakovich and hippie folk 'all held together by the flower-power philosophy'.
'The student cast screamed, stamped and shouted with unbeatable verve while the orchestra played with a panache worthy of Godspell or Jesus Christ Superstar,' wrote the critic Richard Fairman.
Doreen Wright, who has worked for the college for the last 11 years and is the principal's assistant, said: 'It was a nightmare. It is the only time I can recall the whole theatre was stripped right back to the edges to make room.'
But once the scene shifters had turned the theatre into a vast empty warehouse, it was fantastic, she said. The 140-strong choir, orchestra and a jazz band performed in the centre, with the audience squeezed in around the edges. 'It was a massive event.'
The first performance at the Guildhall was conducted by John Mauceri, a New Yorker and protege of Bernstein who is now musical director of the Hollywood Bowl Orchestra. He was with Scottish Opera from 1987 to 1993.
The Guildhall School of Music and Drama has over 700 students studying at under and post graduate level. It also runs opera, jazz and music therapy courses.
Bernstein died in 1990, aged 72. As well as being conductor of the New York Philharmonic Orchestra, he was guest conductor with the Vienna Philharmonic and London Symphony Orchestra.
The complexities of winding up his estate has meant that the Guildhall school learnt only recently of the bequest. The scores have not yet been delivered.
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