The American soprano Judith Nelson, who has died after a long battle with Alzheimer’s disease, was one of the most prominent voices in the early music world at a time when the emergence of period-instrument ensembles was causing a rethink of the kind of vocal sounds and styles required for baroque music.  Her light, clear and agile voice brought the purity of tone and accuracy of line that were very much in demand at the time, yet there was also a discreetly applied vibrato and assiduous attention to diction that lent it grace, radiance and a measure of old-style poise.  

Born Judith Manes in Illinois in 1939, she studied in Minnesota before moving with her English-lecturer husband to Berkeley in 1962, where she sang with the UC Berkeley Collegium and the Berkeley Chamber Singers. In the early 1970s a scholarship took her to Europe, where she formed fruitful working relationships with René Jacobs’s Concerto Vocale (recording Monteverdi and Charpentier for Harmonia Mundi) and the Academy of Ancient Music, for whom she was a principal soloist under Christopher Hogwood and Simon Preston in Decca L’Oiseau-Lyre recordings of Handel (including the groundbreaking 1980 Messiah), Bach’s Magnificat, Haydn masses and Purcell’s theatre music. These, and her work with the Consort of Musicke, also brought her into contact with the young Emma Kirkby, and their sublime duetting in recordings of Handel Italian cantatas, Vivaldi’s Gloria and Couperin’s Leçons des ténèbres is among the most memorable recorded legacies of the time. She loved singing Purcell, and was Belinda to Kirkby’s Dido in Andrew Parrott’s Dido and Aeneas (Chandos), as well as appearing in John Eliot Gardiner’s The Fairy Queen (Archiv). Back in America she took part in another landmark recording of the early 80s, Joshua Rifkin’s one-to-a-part Bach B minor Mass (Nonesuch), the first of its kind.  

The late 80s and early 90s saw her concentrate her work in the USA, where she made regular appearances and recordings with Nicholas McGegan and the Philharmonia Baroque Orchestra, and Jeffrey Thomas and the American Bach Soloists, before illness overtook her.  

Lindsay Kemp