David Daniels emerged in the 1990s as one of the strongest members of a crop of new countertenors. His parents were both voice teachers, and he trained for a number of years as a tenor, but it was not until his decision to explore the countertenor repertory that his voice found its best aspect. He also fell in love with the Baroque repertory, which is the primary source of roles associated with the countertenor voice. He has said that Handel's music has more emotion than even the histrionic verismo school of Italian opera, and he has become particularly associated with the role of Nero in Monteverdi's L'incoronazione di Poppea. He sang it with the Florida Grand Opera in one of his early appearances, and gained international fame in the part with the Glimmerglass Opera's production in 1994, reprising the role with that company at the Brooklyn Academy of Music in 1996.

Daniels' voice is strong and representative of a newer style of more masculine countertenor singing, free of the typical hooty sound of earlier exponents of this voice range. Of his Nero performance, the Wall Street Journal said that he "brought down the house with ferocious coloratura." He debuted with the Glyndebourne Festival Opera in 1996 as Didymus in Handel's Theodora, with stage direction by Peter Sellars, in a performance that was called riveting. He often sings in the most prominent 20th century countertenor role, Oberon in Britten's A Midsummer Night's Dream, which was his London debut role with the English National Opera. His other repertory includes Handel's Tamerlano, Xerxes and Jephtha (his Salzburg Festival debut role), Sesto in Giulio Cesare (his Metropolitan Opera debut role in 1999) and, in concert, an unusual selection of works ranging from Baroque to Britten and including such composers as Debussy, Gounod and Massenet. In 1997 he became the first countertenor to win the coveted Richard Tucker Award., Rovi