While we’re talking, Ellis Marsalis takes two calls and ignores another. Spring in New Orleans is a musician’s busiest time, and not only is Marsalis playing the French Quarter Fest and Jazz Fest, but he’s promoting his new album, An Open Letter to Thelonious (ELM). He and Irvin Mayfield also released Love Songs, Ballads and Standards (Basin Street), and today he’s at NOCCA to teach a master class to his son Jason’s students.