The Complete Opera Book

Various additions were made to it before publication, and also in subsequent editions or reprints, as the subject demands constant revision and renewal, both through new works and through the discovery or revival of lesser known existing ones.

The work in its original form was first finally edited and brought together for publication by Katharine Wright, who at the same time included some additional operas in sections that bear her initials.

The earlier supplement included works by Maeterlinck, Reginald de Koven, Ravel, Henry Hadley, Andre Messager, Holst, Rutland Boughton, Ethel Smyth, Rimsky-Korsakov, Mussorgsky and Stravinsky, and Mozart's Il Seraglio, occupying pp. 851–901.

After 1929 it was enlarged to include Verdi's Simone Boccanegra, Boito's Nerone, Alban Berg's Wozzeck, Puccini's Turandot, Rossini's La Cenerentola, Mozart's Così fan tutte, Jaromir Weinberger's Schwanda the Bagpiper and Vaughan Williams's Hugh the Drover (pp. 901–930).

The English 1935 imprint included Bonavia's notes on Rossini's L'Italiana in Algeri, Rimsky-Korsakov's Snegourochka and two operas of Ildebrando Pizzetti: parts of the former supplement had by now been incorporated into the main text, and the overall page-count before index was now 945 pages.

The great body of Kobbé's work was maintained and enlarged in Part 2, "The Nineteenth Century" (beginning with Beethoven), preserved the original format of the various national "schools", with specific sections on Wagner and Verdi.