The purpose of this study is to investigate the management of tessitura in the choir though the use of choral pivoting in Frank Martin's Messe pour double choeur a cappella (1922), since the ranges of a vast number of choral works extend beyond the limits of what the American Academy of Teacher's of Singing have deemed "best" and "safest." According to the American Academy of Teachers of Singing, many great teachers of singing hesitate to allow their "pupils to participate in choral singing because experience has proven that, due to the unusually high tessituras dominating the arrangements of many choral works, harm is done to the voice. "This study includes an in-depth summary of the anatomy and physiology of the vocal mechanism in specific registers and the potential for harm, vocal strain, or vocal fatigue when singers must sing in an extremely high or low tessitura for an extended amount of time. Three methods of vocal pivoting are examined and explanations given as to how choral pivoting may be applied in Messe pour double choeur a cappella.