http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
pt. 1. Coloratura soprano, lyric soprano, and dramatic soprano.--pt. 2. Mezzo soprano and contralto.--pt. 3. Lyric and dramatic tenor.--pt. 4. Baritone and bass.--pt. 5. Program notes for the Singer's repertoire.
Joint author for volume 5: Werner Singer.