Gayle Wald, Professor of English at George Washington University, is featured in the PBS American Masters episode, "Sister Rosetta Tharpe: The Godmother of Rock & Roll," which premieres Friday night at 10 p.m. Central on SDPB-TV. Wald is the author of "Shout, Sister, Shout! You can learn more about Wald's book at www.shoutsistershout.net.