Ry Cooder’s I, Flathead, is the culmination of his ambitious and fascinating “California Trilogy,” the last of three albums in which the singer and guitarist journeys through the real and imagined history of mid-20th century, multi-ethnic California, sampling the sounds of its barrios and byways, its nightclubs and honkytonks. Cooder assumes the gruff yet chummy voice of Buk, a hard-living, car-racing, guitar-playing man, and the album is subtitled “The Songs of Kash Buk and the Klowns.” Aiding and abetting Cooder in his storytelling is a veritable repertory company of players, including drummers Joachim Cooder and Jim Keltner, accordionist Flaco Jimenez, trumpeter Jon Hassell, singer Juliette Commagere, saxophonist Gil Bernal and engineer /multi-instrumentalist Martin Pradler. Though Cooder is thinking conceptually big, the sound this extended family makes is loose, funky and intimate, incorporating blues, folk, country and primitive rock and roll. With I, Flathead, Cooder brings it all back home, recalling California as it once was, as it might have been, and as it still may sound if, like Cooder, you know where to look.