From the Lower Rio Grande Valley of Texas to East L.A. to the barrios of Chicago, people are listening to the heartfelt, accordion-driven sounds of conjunto. Born in South Texas in the 1920s, conjunto has become popular throughout the United States, Mexico, and, of late, Europe and Japan. But Texas remains the heart of conjunto music making. Indeed, the largest conjunto festival in the world is the Tejano Conjunto Festival en San Antonio, founded...