The literal translation, between Fach, would make the term applicable to any voice that seemed to share characteristics of neighboring categories.
As illustrated in Table 4 below, one Fach may indeed include roles previously deemed the territory of such disparate Facher as coloratura soprano and contralto.
The main American source in recent years for Fach descriptions and role assignation has been the Guide to Operatic Roles & Arias by Richard Boldrey.
Boldrey's book consists of thirty pages of introductory material (in which the categories and criteria used to arrive at them are explained) and a series of intricate listings organized in various ways to aid in searches (listings of roles organized by Fach, alphabetical listings of roles, lists of roles and their Facher organized alphabetically by opera, etc.).
Coming at the list not from casting trends but from pedagogic concerns, as Boldrey has done, is the only way to fulfill the theoretical premise of Fach as protecting the longevity of the singer.
Boldrey's prose descriptions of categories, in contrast to these lists, trace larger conceptions of Fach and the history of the terminology.
Indeed, the Fach system is one in which even a cautious general statement such as that above can be shown too ambitious when taken in a larger temporal context.
Boldrey's lists would naturally include more Fach listings, since he lists greater subdivision of primary categories, yet for many of the roles multiple primary categories are also represented (Idamante, for example, includes soprano, mezzo soprano, countertenor, and tenor).
One of the most important aspects of the Fach system for a teacher to keep in mind is that it represents casting preferences of one particular moment in time.
Table 2, then, offers historical reasons while Table 3 offers pedagogic reasons for investigating the appropriateness of Fach listings as mezzo soprano.
One might therefore say that there exists a great variety of vocal and acting demands in the current lyric mezzo soprano Fach, and that the constant may be in general physical expectations.
Voice classification and Fach are two separate and independent systems of categorization, and the conflation of the two can adversely affect the future career of a singer.