The Southampton Arts Center will kick off its summer music programs with three free outdoor concerts on Saturday and Sunday. Jazz at Lincoln Center’s Jazz for Young People on Tour program will return to the center on Saturday afternoon at 4 with a free performance on the outdoor stage by Thunderswamp, a party jazz collective whose music celebrates the culture and legacy of New Orleans. Compositions by Louis Armstrong, Sidney Bechet, Professor Longhair, and others will be on the program.