Incomplete autograph manuscript, 1916-1928, by Josef Charles Holbrooke of his three-act opera Bronwen (op. 75), being the third and final part of his operatic trilogy The Cauldron of Annwn; Act I is lacking. The libretto, based on the narratives of The Four Branches of the Mabinogi, was written by Holbrooke's patron, Thomas Evelyn Scott-Ellis, eighth baron Howard de Walden.
Mostly composed at Harlech, the work was completed in parts, the Overture (MS 23863F) (published as a piano arrangement in 1917), here dated July 1916 (p. 17); Act II (MS 23864F) dated 5 August 1918 (p. 183); and Act III (MS 23865F), dated 12 October [19]24 (p. 295); the latter is probably the completion date of the full score (confirmed by the note at the end of the published version of 1929), as opposed to the vocal score of the opera, which was apparently completed at Harlech on 5 February 1920 (see note at end of the published vocal score (1922), and cf. George Lowe, Josef Holbrooke and His Work (London, 1920), p. 273). However, a note added at the end of the Prelude to Act III (MS 23865F, p. 190) suggests that a final revision was made in 1928. The vocal score was first published, with English and German words, as Bronwen: A Music Drama (No. 3) (London, 1922), and the full score in 1929 (see British Library Catalogue of Printed Music); the opera was first performed by the Carl Rosa Opera Company in Huddersfield on 1 February 1929.

Stage management and technical information, as well as more general information, relating to past opera productions that will not be revived in future. Files may consist of bound Staff Producers' scores, which record the stage movements, translations and music cuts of each production (including any revivals), and usually contain set plans and designs; bound Stage Managers' prompt scores which record the cues (lighting, curtain, electrical, crew and singers') used for 'calling' the show from the side of the stage. Material may also include stage lists and instructions, cast and chorus lists, props lists, weapons lists, wing running lists, set and costume designs, small-scale plans and stage diagrams, production photographs, librettos, call sheets, smoke plots, cue plots, fly plots, scene breakdowns, letters and internal memoranda regarding production meetings and details of production, playbills, programmes, and opening night/good luck cards.