Beecham, BEE chuhm, Sir Thomas (1879-1961), a British conductor, became one of the world's influential musicians, even though he received little formal musical education. During a period of 40 years, he became a major force in the musical life of Britain. Beecham specialized in opera. He vigorously supported little-known music and founded and financed major orchestras and opera companies. He was known for his irreverent wit and for his expressive flair on the podium.