Frederick Delius' instinctive feel for Negro music and the use he made of it--as Mrs. Jahoda points out, it was he, not Gershwin, who wrote the first Negro opera--give him a particular pertinence; his incredibly crowded, precipitous, poignant life makes him a natural for biography regardless. His father, a prosperous Yorkshire wool merchant of German origin, was contemptuous of his absorption in music; he would never be a composer, Delius, Sr. said, and to the end his mother never acknowledged that he was. After a few years of parrying--Fritz neglecting business for music in England, Germany, Norway, France--the two settled on a scheme for Fritz to grow oranges in Florida: he would be busy and away from music. But Solano Grove turned out to be a jungle, its only yield the songs of the Negro tenant family which Fritz, in a moment of ""illumination,"" took as the key to his life's work. The American period--faced with an ultimatum from his father, Delius supported himself as violin teacher and Sabbath Cantor in roaring (1885) Jacksonville, as ""Celebrated Professor"" of almost everything at a girls' academy in Danville, Va.--has a vitality only slightly diminished by the author's decorousness. A quality you appreciate when, after his belated recognition, Delius becomes a blind paralytic, then, sheltered by his wife and assisted by a young English musician, rallies to dictate music again. Mrs. Jahoda has gone to the sources and knows music; hers, moreover, is the only Delius biography by an ""outsider."" Whether for adults or young people (who may need some encouragement), it should be a revelation; it is certainly a tribute to tenacity.