Taddei was born in Genoa, Italy, and studied in Rome, where he made his professional debut in 1936 as the Herald in Wagner's Lohengrin.
The following year, 1948, saw his debut at the Salzburg Festival, La Scala in Milan, and the Teatro di San Carlo in Naples.
His acting repertoire included the two Figaros, from The Marriage of Figaro and The Barber of Seville, both Leporello and Don Giovanni in Don Giovanni, both Belcore and Dulcamara in L'elisir d'amore, as well as Don Carlo in Ernani, Macbeth in Macbeth, Rigoletto in Rigoletto, Amonasro in Aida, Iago in Otello, Falstaff in Falstaff, Barnaba in La Gioconda, Gérard in Andrea Chénier, and Scarpia in Tosca, among others.
His vocal longevity allowed him to continue singing into old age, including a debut at the Metropolitan Opera, on 25 September 1985, in the title role of Falstaff, at the age of 69.
[2] Taddei left many recordings, notably as Figaro in The Marriage of Figaro and Leporello in Don Giovanni in the Carlo Maria Giulini renditions, as Macbeth, opposite Birgit Nilsson, in Macbeth, conducted by Thomas Schippers, and as Scarpia in Tosca and as Falstaff in Falstaff, both conducted by Herbert von Karajan.