Capitalization of key, opus, and number

Music Cataloging at Yale

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Capitalization of Key, Opus, and Numbers

See also Capitalization of foreign terms

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

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)
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

Number:

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