Adolf Busch, the greatest German violinist of the 20th century, is now known only to classical-record collectors who treasure the searchingly eloquent 78s that he cut with Rudolf Serkin, his son-in-law and recital partner, and the Busch Quartet, the ensemble that he led for three decades. But there is another reason to remember him, one that in the long run may well count for as much as the music that he made: Mr. Busch's name is at the very top of the short list of German musicians who refused to kowtow to Adolf Hitler. This latter aspect of his life is described in detail in Tully Potter's "Adolf Busch: The Life of...