Strauss and Furtwängler. Only three of those recordings are known to still exist. This includes a performance of Beethoven's "Emperor" Concerto with pianist Walter Gieseking and the Berlin Reichssenders Orchestra conducted by Artur Rother. This remarkable performance was later issued on LP by Varèse Sarabande. Later in 1993, the Audio Engineering Society (AES) issued a special CD for the 50th birthday of stereo recording. This CD not only includes the "Emperor" Concerto, but the two other stereo recordings known to exist: a Brahms serenade and the last movement of Bruckner's 8th Symphony conducted by Herbert von Karajan. Piano Library also issued the Emperor concerto, and Iron Needle issued the Bruckner recordings (catalog IN 1407). ArkivMusic released a CD of the concerto, as well a later recording Gieseking made of Beethoven's first piano concerto with the Rafael Kubelik and the Philharmonic Orchestra. Magnetophon recorders were widely used in German radio broadcasts during World War II, although they were a closely guarded secret at the time. The Allies were aware of the existence of the pre-war Magnetophon recorders, but not of the introduction of high-frequency bias and PVC-backed tape.) their intelligence experts knew that the Germans had some new form of recording system but they did not know the full details of its construction and operation until working models of the Magnetophon were discovered during the Allied invasion of Germany during 1944-45. American audio engineer Jack Mullin acquired two Magnetophon recorders and fifty reels of magnetic tape from a German radio station at Bad Nauheim near Frankfurt in 1945. The allied forces were traveling through Germany during WWII when they first discovered the device. The Allies then handed the Magnetophon over to Mullin. Over the next two years Mullin modified and developed these machines, hoping to create a commercial recording system that could be used by movie studios. American popular vocalist Bing Crosby, dissatisfied with the quality of existing radio network recordings was prevailed upon to invest in this development and would use the technology, as modified by Mullin and the fledgling Ampex company, to record his radio broadcasts in the more relaxed atmosphere of the recording studio, which was a significant break from the then-norm of live studio audience broadcasts. In 2008, at the 50th Annual Grammy Awards Ceremony, Ampex received the company's first Grammy Award for Technical Achievement, to honor their contribution sixty years earlier of the Ampex 200, which