Grau studied at the Escuela de Música José Ángel Lamas and the Escuela de Música Juan Manuel Olivares in Caracas under Vicente Emilio Sojo, Ángel Sauce, Juan Bautista Plaza, Gonzalo Castellanos, Luis Felipe Ramón y Rivera and Robert Fountain. He later took courses in orchestral conducting under Sergiu Celibidache in Bologna (1972-73) and Bernard Keffe in London (1977-78) and in composition and orchestration under Patrick Stanford (1977-78).
In 1967, he founded the ''Schola Cantorum of Caracas'', with which he won first prize at the International Guido D'Arezzo Competition in Italy in 1974 and made numerous recordings. He was also the founding director of the Orfeón Universitario Simón Bolívar (1970). After teaching at various music schools in Caracas, he was professor of choral conducting at the Instituto Universitario de Estudios Musicales (IUDEM) from 1979 to 2001 and at the Universidad Simón Bolívar from 1996 to 2001. He was also head of the choral symphony department of the Fundación Orquesta Nacional Juvenil de Venezuela. Grau has worked as a guest lecturer in the USA, Spain, Sweden, Israel, Argentina and Brazil.
As a composer, Grau was awarded the Premio Nacional de Música José Angel Montero three times: in 1967 for ''Tríptico para Mezzo y Piano'', in 1983 for ''Dies Irae'' and in 1987 for ''Pater Noster'' for mixed choir. His ballet ''La Doncella'' won first prize at the Día Internacional del Canto Coral in Barcelona in 1978. With the Opereta ''Ecológica en Cuatro Actos'', Grau won the Premio de Composición y Expresion Coral of the Government of the Canary Islands in 1999.
