(It.: ‘closed mouth’; Fr. bouche fermée; Ger. Brummstimme).
Singing without words and with the mouth closed: that is, humming. Especially in choral passages, the effect can be magical, and composers have used the technique for special colouration. Puccini’s use of a humming chorus in the interlude of Act 2 of Madama Butterfly poignantly marks the passage of Butterfly’s waiting. Verdi uses this choral effect in the storm scene of the final act of Rigoletto. Villa-Lobos’s Bachianas brasileiras no.5 makes a rare use of bocca chiusa for solo voice.
In comic opera singers are sometimes called on to sing with their mouths obstructed, such as in Die Zauberflöte where Papageno sings with a padlock on his mouth, but that is not a true use of bocca chiusa. Although untexted singing has become more common in the 20th century, often this is not hummed but sung on one or more vowels (see Vocalise). The female humming chorus in Holst’s The Planets, which aids in the depiction of Neptune, ‘the mystic’, for example, is not marked bocca chiusa, and at least some editions suggest that the vocal lines be sung on the vowel ‘u’ as in ‘sun’. Similarly, the solo vocalization in Vaughan Williams’s Pastoral Symphony is not marked bocca chiusa.
ELLEN T. HARRIS