Capitalization of key, opus, and number

Music Cataloging at Yale [1] ♪ Language tools [2]

Note: These instructions apply to recording information for title and contents notes in bibliographic records and 670 field [3] in authority records. They do not apply to authorized access points for music.

Key:

In English, the key is capitalized, but not the mode: A major, D minor.
In German¹, D in Dur and M in Moll are capitalized.
- In major, the key is capitalized: D-Dur, Fis-Dur
- In minor, it is not capitalized: a-Moll, fis-Moll
In other languages,
- when given as a letter, the key is capitalized: F majeur, G mineur
- but when given as a word, it is not capitalized: fa majeur, sol mineur.

Symphonie Nr. 2 C-Dur op. 61
Konzert für Violoncello und Orchester a-Moll, op. 129
Messe in Es op. 155
Concerto in A minor (Wq 166, H 431) for flute, strings and basso continuo
Sonata per cembalo in sol maggiore
Koncert C dur² pro fagot a smycce

The LC Music Division's Bibliographic Access Section's policy regarding transcription and recording of statements of key that are in German:

The words "Dur" and "Moll" will always be capitalized.
Letters and initial letters with suffixes indicating flats and sharps (-is, -es) will be in upper case when preceding "Dur" and in lower case when preceding "Moll".

Source: e-mail on NMP-L from Damian Iseminger, Head, Bibliographic Access Section, Music Division, Library of Congress, dated 10/11/2018

¹This policy is based on a 1977 LC memo stating that, regardless of how a word appears on the publication, for German capitalization, follow Duden Rechtschreibung der deutschen Sprache und der Fremdwörter (Mannheim : Bibliographisches Institut, c1986) It is unknown if LC is applying this policy in RDA
²D in dur is not capitalized here because it is not in German.

Opus:

In German¹, opus is capitalized when spelled out, but not when abbreviated: Opus, op.
In other languages, neither is capitalized.

Vier Fugen Opus 72
String trio opus 45
Symphonies Nr. 2 C-Dur op. 61
Quartet op. 73 for 2 violins, viola, and cello

Numbers:

In German¹, number and its abbreviations are capitalized: Number, Nr., No.
In other languages, it is not: number, no., nr.

Duo concertant für zwei Klarinetten op. 3, Nr. 1
Fantasie für Klavier ohne D-Nummer = Fantasy for piano without "D" number
Quartet No. IV für 2 Violinen, Viola & Violoncello, op. 40
Sonata in D major op. 2 no. 2