Singer/songwriter Will Johnson masterminded this split double CD as a way to unite both of his decade-old bands. Centro-matic rounds out scraggly Southern rock with power pop, balancing neurotic pain and desperate joy on loose-limbed rockers such as “Twenty-Four” and “Quality Strange,” framed by Johnson’s gorgeously aching voice. South San Gabriel (basically Centro-matic plus guests) goes for calmer, prettier alt country, decorated with elegant strings. The haunted a cappella of “My Goodbyes” and the melancholy images of “Alabama Crusade” recall prime Elliott Smith. Opening for Drive-By Truckers is Johnson’s reward, but you wish that DBT were as ambitious nowadays.