In 1970 Sadie was appointed by the publisher Macmillan to begin work on a sixth edition of 'Grove's Dictionary of Music and Musicians', published in 1980 as 'The New Grove Dictionary of Music and Musicians', in twenty volumes. Not only was the sixth edition on an unprecedented scale, but it embraced topics new to musicology (including world music, ethnomusicology, ancient music, sources, analysis, popular music) and was written by an international team of specialists.
The sixth edition generated several other reference works with which Sadie was involved, notably 'The New Grove Dictionary of Musical Instruments' (3 vols., 1984), 'The New Grove Dictionary of American Music' (with H. Wiley Hitchcock; 4 vols., 1986), 'The Grove Concise Dictionary of Music' (1988), 'The New Grove Dictionary of Opera' (4 vols., 1992), and 'The New Grove Book of Operas' (1996). Sadie was later co-editor, with John Tyrrell, of the seventh edition of the main dictionary (29 vols., 2001).
Contains correspondence and related papers concerning Sadie's employment at Macmillan and editorship of 'The New Grove Dictionary of Music and Musicians' and other reference works; articles and lecture notes by Sadie on the New Grove dictionaries; reviews of the New Grove publications.