Gaetano Guadagni (16 February 1728 – 11 November 1792) was an Italian mezzo-soprano castrato singer, most famous for singing the role of Orpheus at the premiere of Gluck's opera Orfeo ed Euridice in 1762.
Born at Lodi, Guadagni joined the cappella of Sant'Antonio in Padua in 1746, but also made his public operatic debut at Venice that year, which did not meet with ecclesiastical approval: he was dismissed from his position in Padua by 1748, and soon after appeared in London as a member of Giovanni Francesco Crosa ("Dr Croza")'s buffo (comic) company. He does not appear to have had the typical rigorous training that most castrati undertook (see castrato), which may account for his being described by the music historian Charles Burney as a "wild and careless singer" on his arrival in England. He was rapidly taken up in theatrical and musical circles in the capital, and also acquired a reputation for his sexual activities, as did many castrati. This was reported by Horace Walpole in a letter to Horace Mann dated 23 March 1749:
Delaval, a wild young fellow, kept an Italian woman, called the Tedeschi. He had notice one day that she was actually then in bed with Guadagni, a handsome young eunuch, who sings in the burlettas. The injured cavalier takes one of his chairmen and a horsewhip, surprises the lovers, drags them out of bed, and makes the chairman hold Mars, while he flogged Venus most unmercifully. After that execution, he takes Guadagni, who fell on his knees and cried and screamed for mercy – 'No, Sir, said Delaval, 'I have another sort of punishment for you', and immediately turned up that part, which in England is accustomed indeed to be flogged too, but in its own country has a different entertainment – which he accordingly gave it.
For performances in 1750 Handel rewrote three arias in Messiah for him, the first, "But who may abide", being particularly adapted to a castrato's bravura technique (which he clearly had acquired by this date). Handel had previously set this text as recitative, and then as a comparatively gentle minuet in triple time throughout. Both of these were for bass voice: for Guadagni, as well as transposing the first section up an octave, Handel wrote a new, virtuosic setting of the text "For he is like a refiner's fire", especially exploiting the singer's fine low notes. Guadagni also took part in revivals of Samson (for which Handel reworked a part originally written for Susannah Cibber), Judas Maccabeus, Belshazzar and Esther. The one role that Guadagni actually created for Handel was Didymus in Theodora. Where Messiah had exploited his virtuosity in rapid passage work, this new role gave him, at the beginning of the aria "The raptur'd soul", a fine opportunity to display his "artful manner of diminishing his voice like the dying notes of an Aeolian harp", as Burney described it. The latter also claimed to have helped Guadagni with his English, saying that, "during his first residence in London he was more noticed in singing English than Italian". In 1755, he was engaged by David Garrick to sing in an English opera The Fairies by Handel's sometime amanuensis, John Christopher Smith, and the famous actor, again according to Burney, "took much pleasure in forming him". At this time his voice was described by Burney as a "full and well-toned countertenor (here meaning that his range matched that of the contemporary English voice of that name; however, the historian was mistaken in his perception that Guadagni's voice changed from alto to soprano in later life). Burney also remarked on unusual details in the manner of Guadagni's performance: "attitudes, action and impassioned and exquisite manner of singing the simple and ballad-like air Che farò [in Gluck's Orfeo ed Euridice, see below], acquired his very great and just applause".