He entered one of the leading vocal competitions, the 1978 's-Hertogenbosch Competition in the Netherlands, and won the First Prize, establishing his international career. In the meantime, he was one of the three co-founders of the Hilliard Ensemble, which was formed in 1974. The Ensemble became a noted force in the early music movement, specializing in music written before 1600. The group, a vocal quartet for most of its existence, came to find points of similarity between the freely polyphonic music of the Renaissance, with its frequent complex harmonies and dissonance, and the newer tonal music being written in its own time. They have premiered a considerable amount of new music by such composers of Arvo Pärt, Elena Firsova, James MacMillan, Stephen Montague, Veljo Tormis, Heinz Holliger, Edward Cowie, John Tavener, and Gavin Bryars, and worked with the improvisatory Norwegian saxophonist Jan Garbarek. Many of its recordings of this repertory are on the ECM New Series label.
He sang and recorded the alto arias in the reconstruction of Bach's Passion According to St. Mark with the European Community Baroque Ensemble and participated in a recording of Giya Kancheli's Third Symphony with the London Philharmonic on the EMI label.
David James also has sung with the larger vocal ensemble The Sixteen. His sweet and distinctive countertenor tone is credited as a major factor in the success of both groups. With The Sixteen he has recorded J.S. Bach's Passion According to St. John, Handel's Messiah, and Bach cantatas. He is in demand for operas with countertenor roles, which include many Baroque ones and a few modern operas, including Britten's A Midsummer Night's Dream. He has sung major roles with the English National Opera, the Handel Opera, the Geneva Opera, and the Aldeburgh Festival.
As a solo singer he sings a wide range of pre-Classical and contemporary repertoire. He frequently works with Heinz Holliger (recording for ECM and widely singing Holliger's song cycle Beiseit) and Gavin Bryars, singing in the world premiere of Bryars' opera Dr. Ox's Experiment with the English National Opera, and recording several others of Bryars' compositions.