He looked like a Calvinist minister. The stern gaze of this intense white-haired eagle-beaked man radiated absolute seriousness of purpose. The austerity of his playing could certainly match it. But Leonhardt's playing could belay his reputation completely. Leonhardt's playing was stern and dull, except when it wasn't. A member of the original period instrument generation and trained in the era when Toscanini and Schnabel were thought the great musical models, his commitment to the Urtext in comparison to his successors was nearly fanatical. Ornamentation was sparing, and rubato judicious and usually the micro-level - rubato in the truest sense of the word. His musicmaking was the precise opposite of the ostentatious ebulliance one finds in a successor like Ton Koopman - his commitment to seriousness was absolute.
(Just a month before he died. Bach's b-minor suite "Fur dans Lautenwerk." Masterly to the end.)
It was in the Postwar Vienna of Harry Lime that the bourgeois Dutch Leonhardt, then a conducting student, met a Viennese aristocrat of roughly the same age named Nikolaus Harnoncourt. Harnoncourt was a cellist who would not conduct in a traditional manner for nearly another twenty years. They began to perform together and when Harnoncourt founded the Concentus Musicus Wein, Leonhardt was his keyboardist. But Leonhardt clearly differed from Harnoncourt in his philosophy and the differences became more pronounced as they got older. Harnoncourt was that of an extraverted performer who believed that research into old styles should be used as a conduit to inform more effective performances in both old and new styles. Leonhardt's approach was that of an introvert and historian, he wanted to recapture the pure style of old music and keep it as a private world, utterly separate from the goings on of other musical styles. By 1955, Leonhardt had moved back to Amsterdam and with him began the fruition of an entire Dutch school of early music with the founding of the Leonhardt Consort: Ton Koopman, Franz Bruggen, and all three Kuijken brothers were either conducted or taught by him. He even had an important effect on the English early music scene by being one of the principal keyboard teachers of Christopher Hogwood and a favored conductor for the English countertenor - Alfred Deller. His principal achievement as a conductor was to come later in of the most momentous recording projects in music history. Together with Nikolaus Harnoncourt, he recorded the complete cantatas of Bach. It began in 1971, and took them until 1990!
(Leonhardt conducting the opening chorus of the St. Matthew Passion in 1967. Dressed as Bach...an eerie, eerie clip)
Like most period specialists, he made a particular specialty of Bach, whose music he conducted and played on both the harpsichord and organ. He was particularly at home in the Renaissance Baroque work of Northern Europe - Bach predecessors and contemporaries like Telemann, Purcell, Buxtehude, Biber, Byrd, Froberger and his compatriot Sweelinck were all important composers to him. However, he did reserve an intense dislike for Handel, whom he regarded as a panderer to mass tastes. He performed works of the French Baroque, but the greater flash demanded in these works did not suit the austerity of his temperament particularly well, and Leonhardt said as much in interviews, deriding them as 'superficial.' He had a similar attitude towards popular music, which he claimed was based entirely on 300 year old musical developments. Leonhardt was an artist who made war with frivolity. The results could be dry, they could also be life changing.