Scope and arrangement
The Hubert Mengelbier scores consist almost entirely of full scores, parts, or sketches for about 50 works, all either manuscripts or manuscript copies. Among them are vocal/orchestral works such as Ich bin der Dokter Eisenbart, Kantate wann der jungste Tag will werden, Sternennacht, Parodie, and many vocal trios, duets, and solos with piano accompaniment; orchestral works such as Serenade für Orchester mit dem Pfeil dem Boben, Ballet Suite, Weihnachts-Ourertüre, and Hermann der Cherusker Ourertüre für grosses Orckester; and chamber works such as Tanzfolge für sieben Solo Instrumente. Mengelbier's stage works are not present in this collection. A manuscript for at least one of them is held by the University of Cologne.
The collection also holds a small biographical file consisting of clippings, correspondence, a photograph, and a biography translated from a reference book on German composers. The rest of the file's content is in German.
Arrangement
The score arrangement was dictated by a brief listing of Mengelbier's music found in the collection's biographical file, which divides the scores into arrangements of music by other composers, instrumental music, stage music, and vocal music. Scores were arranged alphabetically within those divisions. Titles are not listed individually unless they make up the contents of an entire box.