Dr. Erin Hackel is an Associate Professor at the University of Colorado, Denver. She has founded two award-winning a cappella groups, MIX and Lark, who have been praised for their innovation and have been singled out for their boundary-changing work in collegiate a cappella. Both groups have been BOSS and SoJAM champions, are recipients of multiple performance awards, and have won several Contemporary A cappella Recording awards. Dr. Hackel has published widely on the topics of healthy belt voice singing and historic female singers at the turn of the twentieth century.