Thrum boasts four new contemporary works for this unusually successful classical guitar quartet: “Ghetto Strings” by Daniel Bernard Roumain, “Thrum” by David Evan Thomas, “Cinema Castaneda” by Van Stiefel and “Guanxi Impressions” by Gao Hong. Roumain’s suite, named after locations known for their urban hardships, is melodically memorable and contains just the slightest hint of fire. The title suite, while less abrasive, glows with the thematic gifts of a contemporary classical style in search of a new expression while never forgetting the old ways. “Cinema Castaneda” is when the music starts to go into Windham Hill territory, bridging the lush pines to arid ranches and the subtle madness that comes with it. And on “Guanxi Impressions”, Joseph Hagedorn, Maja Radovanlija, Wade Oden and Ben Gateño are joined by the piece’s composer on his pipa, making for a safe if pleasant East-meets-West mashup. With the exception of “Guanxi Impressions”, which is just okay, Thrum is a delightfully mysterious product from a group that really knows how to pull the right commissioning strings.