Although Lawrence Welk may have made the accordion uncool for most, zydeco and conjunto norteñ#o enthusiasts know better. The latter squeezebox-based style, which comes from the Texas-Mexico border region, will be represented in this latest “Musica de las Americas” concert by Flaco Jimenez and Valerio Longoria. Jimenez has popularized the traditional Tejano sound by melding it with rock, blues, and country. On his recent Said and Done, Jimenez adds bouncy, rhythmic fills to the pop-country title track, upbeat Tex-Mex numbers, and sappy ballads. Opening for Jimenez will be the grandfather of conjunto, the 75-year-old Longoria, and the guitar-playing grandmother of the style, 83-year-old Lydia Mendoza. The performance begins at 7:30 p.m. at George Washington University’s Lisner Auditorium, 730 21st St. NW. $15-20. (202) 994-6800. (Steve Kiviat)