On leaving East Germany in 1971, Klaus Tennstedt sought asylum in Sweden. He conducted in Göteborg and Stockholm, where he regularly worked with the Göteborg Theatre and the Swedish Radio Symphony Orchestra. In 1972 Tennstedt became General Music Director of the Kiel Opera in Northern Germany and from 1979 to 1982 he was Chief Conductor of the North German Radio Orchestra in Hamburg.
In 1974, Tennstedt made his first American appearances with the Toronto Symphony Orchestra and the Boston Symphony Orchestra. The success of his visit led to numerous invitations to conduct other orchestras, including performances at the Tanglewood Festival in 1975. Tennstedt regularly returned to Tanglewood where he was greatly admired for his performances of the Beethoven Symphonies and Concertos. He made his USA opera debut in 1983 at The Metropolitan, New York, with performances of Fidelio and continued to conduct many USA orchestras including the New York Philharmonic, the Chicago Symphony Orchestra and the Philadelphia Orchestra till his retirement.
Tennstedt made his London debut with the London Symphony Orchestra in 1976. The following year he made his first appearance with The London Philharmonic and became its Principal Guest Conductor in 1980. In 1983, Tennstedt succeeded Sir Georg Solti as Principal Conductor and Music Director of The London Philharmonic and when he retired he was appointed Conductor Laureate. Tennstedt has also appeared at the Salzburg Festival where he made his debut in 1985 with the Berlin Philharmonic Orchestra, conducting Haydn's Die Jahreszeiten. Due to ill-health Tennstedt retired from conducting in 1994 and died on 11 January, 1998.
Klaus Tennstedt recorded exclusively for EMI Classics from 1977 and his last agreement with EMI Classics was signed in 1992. In November 1992 EMI Classics re-released Tennstedt's celebrated cycle of Mahler Symphonies, recorded between 1977 and 1986. Symphony No.8 from this cycle won a Gramophone award in 1987 and a performance of this work with the London Philharmonic at the Royal Festival Hall in 1991 is available on DVD. 1992 saw the release of Mahler's Das Lied von der Erde with Agnes Baltsa, Klaus König and The London Philharmonic and the Beethoven Violin Concerto with Nigel Kennedy and the Norddeutscher Rundfunk Sinfonieorchester, recorded live at a concert in Kiel, Germany.
Other recordings in Tennstedt's discography include the Beethoven and Bruch Violin Concertos with Kyung-Wha Chung; the Brahms Violin Concerto with Nigel Kennedy and The London Philharmonic; Ein deutsches Requiem by Brahms and Schumann's Requiem; Symphony No.8 by Bruckner with The London Philharmonic; Strauss' Also Sprach Zarathustra and Don Juan with The London Philharmonic and Music from The Ring with The Berlin Philharmonic and scenes from Tristan und Isolde, Tannhäuser, Der fliegende Holländer and Götterdämmerung with Jessye Norman and The London Philharmonic.