Zwischen in the German language means `between,' and over the past century, as operatic voices have evolved in both range and size, the voice classification of Zwischenfach has become much more relevant - particularly to the female voice. Identifying whether nineteenth century composers recognized the growing opportunities for vocal drama, size, and range in singers and therefore wrote roles for `between' singers; or conversely whether, singers began to challenge and develop their voices to sing the new influx of romantic, verismo and grand repertoire is difficult to determine. Whichever the case, teachers and students should not be surprised about the existence of this nebulous Fach. A clear and concise definition of the word Fach for the purpose of this paper is as follows: a specific voice classification. Zwischenfach is an important topic because young singers are often confused and over-eager to self-label due to the discipline's excessive labeling of Fachs. Rushing to categorize a young voice ultimately leads to misperceptions. To address some of the confusion, this paper briefly explores surveys of the pedagogy and history of the Fach system. To gain insights into the relevance of Zwischenfach in today's marketplace, I developed with my advisors, colleagues and students a set of subjects willing to fill out questionnaires. This paper incorporates current interviews from two casting directors of national and international opera houses, an emerging American mezzo-soprano, a mid-career working European mezzo-soprano, an operatic stage director, an education director for opera houses and a composer. These interviews, along with modern examples of zwischenfach voices are analyzed and discussed.