As historical documents, Broadway cast recordings preserve the performances of the original singers fresh from the stage, but as record albums they were conceived to be satisfying in purely aural terms. So, while a cast recording may be known to a far larger audience than ever experienced the show in the theatre, what listeners actually hear is, in the vast majority of cases, a paradoxical kind of authenticity: the original cast performing an abridged version of the music, with little or no dialogue, and with numbers sometimes presented in a different order (in the days of long-playing records, a strong ending to side one and beginning to side two were further conditioning factors). Since it is usually the cast album that provides the most lasting and most widely known documentation of a show in its ‘original’ form, it is worth considering the musical alterations made to transform it into a successful recording, and the case of West Side Story provides an unusually well documented ‘personal take’ on a famous example of the genre. Composers of shows are almost always present at recording sessions, but in this case Leonard Bernstein had to be away in Israel, and the happy consequence for later historians is that Stephen Sondheim, who wrote the lyrics, provided him with an unusually detailed report of the sessions. Goddard Lieberson – the producer of the album – also wrote to Bernstein, giving his first reactions to the musical before its Broadway opening.