In the postwar era, dozens of the world's best-known conductors have led the orchestra. Among them were not only Walter, Furtwängler, Knappertsbusch, Krauss, Szell, Klemperer, and Krips, but also John Barbirolli, Carlo Maria Giulini, Erich Kleiber, James Levine, Zubin Mehta, Fritz Reiner, Georg Solti, Claudio Abbado, Riccardo Muti, Nikolaus Harnoncourt, Lorin Maazel, Mariss Jansons, Daniel Barenboim, Gustavo Dudamel, Roberto Carnevale, Valery Gergiev and Franz Welser-Möst. The orchestra made their first US tour in 1956 under the batons of Carl Schuricht and André Cluytens. Three conductors were given honorific titles by the orchestra in the later 20th century: Karajan and Karl Böhm, who were made Honorary Conductors, and Leonard Bernstein, who was made an Honorary Member of the orchestra. Pierre Boulez, who had conducted the orchestra often, was made an Honorary Member in 2007. Clemens Hellsberg wrote of the "contrast between those dry numbers and the defining experience which each encounter with this brilliant interpreter represented."