Vanguard released a series of important classical recordings, both domestically produced and imported. Many of the latter came from the British label Pye Records label, with performances by the Halle Orchestra conducted by Sir John Barbirolli. The recordings were so exceptional in their stereo sound and overall quality that many classical radio stations played them. Vanguard even released some classical quadraphonic recordings in the early 1970s, including a performance of Tchaikovsky's Fourth Symphony with the American Symphony Orchestra conducted by Leopold Stokowski. The label also released many performances by the Utah Symphony Orchestra conducted by Maurice Abravanel, as well as the earlier P.D.Q. Bach recordings, from 1965 to 1983. Vanguard was the first US label to issue the complete 1944 hi-fi recordings of composer Richard Strauss conducting the Vienna Philharmonic Orchestra in most of his symphonic poems; the recordings were made on the Magnetophon tape recording equipment in the Vienna Opera House.