The German bass has died in Dresden, the city of his birth, at the age of 92. His long career stretched over some 40 years and took him to the world's great opera houses. He studied with Rudolf Dietrich in Dresden, making his stage debut there as the Hermit in Weber’s Der Freischütz at the Semperoper in 1949. In 1952 he joined the company of the Berlin State Opera and also appeared at Bayreuth for the first time. Wagner would form a cornerstone of his repertoire with the title role of Der fliegende Holländer being his most-performed Wagner role. Down the years he would perform Heinrich (Lohengrin), Titurel and Amfortas (Parsifal), Fasolt (Rheingold) and Wotan (Der Ring), Hans Sachs and Veit Pogner (Meistersinger) and the Dutchman. 

In 1967 he made his first appearance at Covent Garden as Wotan; his Salzburg debut followed in 1969 with Baron Ochs in Der Rosenkavalier, a role he performed on numerous occasions and that same year he debuted at the Met as Hans Sachs. Later in 1969 he would again appear at the Met as Wotan in the Ring cycle conducted by Herbert von Karajan. He appeared at the Vienna State Opera in 253 performances embracing 29 different roles; his last appearance there was as the Music Master in Richard Strauss’s Ariadne auf Naxos in 1997. 

He also created a number of new roles, notably in Luciano Berio’s Un re in ascolto (1984), in Paul Dessau’s Einstein (1974), Friedrich Cerha’s Baal (1981).

On record, Adam can be heard in many of his best-known roles including in Beethoven's Fidelio in recordings under Kurt Masur, Leonard Bernstein (twice), Karl Böhm, Sir Georg Solti and Lorin Maazel; in Wagner’s Der Ring under Böhm, Marek Janowski, James Levine and Bernard Haitink, as the Dutchman (Otto Klemperer), in Meistersinger (Karajan), as Wozzeck (Herbert Kegel and live under Carlos Kleiber), as Sarastro in Mozart’s Die Zauberflöte (Sawallisch, Otto Suitner and Sir Colin Davis). He often performed and recorded oratorio and can he heard on record in Bach cantatas, St Matthew Passion and Christmas Oratorio, Haydn’s Die Schöpfung, the Mozart Requiem (on Gramophone's 1984 Choral Award-winning Philips recording under Peter Schreier) and Mendelssohn’s Elijah (for Sawallisch: ‘From his entry at the very start of the work, Theo Adam exerts his authority and presents the epitome of an Old Testament prophet, at once implacable and tortured. It is a portrait drawn superbly by Mendelssohn in Elijah's four solos, and Adam is as adept in the Handelian runs of "Is not His word?" as in the aching doubt of "It is enough", wrote Alan Blyth in February 1988.)