Conti was born in Arpino in 1714, possibly the son of the composer Nicola Conti. After studying in Naples with Domenico Gizzi, after whom he would later be nicknamed, he made his debut in Rome at an early age, around 1730. According to some modern encyclopedic sources, it took place in Leonardo Vinci's Artaserse, which premiered on 4 February at the Teatro delle Dame. However, his name does not appear in the cast of the original libretto, and his theatrical debut ought probably to be dated instead in 1731, in revivals of Didone abbandonata and of the same Artaserse, both by Vinci. A colourful anecdote relates how another overweening castrato star, Caffarelli, rode post-haste to Rome from Naples just to attend incognito his debut; and full of enthusiasm eventually yelled at him: "Bravo, bravissimo Gizziello, it’s Caffariello who's telling you!" Whatever the case, at the beginning of 1732 he was urgently called upon to replace the castrato Nicolò Grimaldi, who suddenly died on 1 January during the rehearsals of Pergolesi's first operaLa Salustia at the Teatro San Bartolomeo in Naples. Having become a member of the theatre's company, later that year he performed in new operas by Johann Adolf Hasse, Leonardo Leo and Francesco Mancini, and in revivals of Vinci's Catone in Utica and Artaserse. His subsequent career led him throughout Italy, as well as abroad. In 1736–37 he was in London, where he had been engaged by George Frideric Handel, with whom he would build a profitable collaboration. Conti performed in many of his works, such as Atalanta, Giustino, Berenice and Arminio, as well as in a revival of Ariodante. He sang at many premieres for the best and most famous musicians of his time, including Niccolò Jommelli, Baldassare Galuppi and Johann Adolf Hasse. After 1759, Conti left the stage and settled in Rome, where he spent the last two years of his life. Being a very sharp soprano for his time, Conti was not quite well disposed towards abuse of coloratura and he chose rather to turn to better account his fluent and smooth style of rendering and expression: he has thus remained famous as a sentimental and gentle singer, but he also always kept a condition of absolute excellence at vocal virtuosity, even though not so acrobatic as, for instance, that of his contemporary Farinelli.
