Many choral teacher-conductors and voice professionals utilize semioccluded vocal tract (SOVT) exercises (e.g., lip trills, straw phonation) in their classrooms or studios. Research with individual singers has indicated that these techniques may increase "vocal economy," boosting acoustic output while reducing singer effort. Recently, researchers have investigated these phenomena in choral settings, finding that choirs have maintained or increased spectral energy after straw phonation. Most chorister participants have perceived improved choral sound and vocal efficiency after the protocols. These investigations, however, have used one-group pretest-posttest designs. Therefore, results could reflect a "masterclass effect." The purpose of this study was to compare acoustic output and listener perceptions of pre- and posttest measurements of two matched women's choirs who engaged in (a) a straw phonation protocol or (b) an identical protocol performed on a neutral, unoccluded vowel ("ah"). Results indicated that both groups sang with more spectral energy after the protocols, and a majority of expert listeners noted these increases. However, the straw group's increase was more than 1 dB SPL greater across the entire spectrum (0--10 kHz). Choral teacher-conductors and music teacher educators may wish to use straw phonation exercises to increase choral output and reduce vocal effort.