Voice classification in non-classical music chart that follows. The ranges given below are approximations and are not meant to be too rigidly applied. Some men, in falsetto voice or as a result of certain rare physiological conditions, can sing in the same range as women. These do not fall into the female categories, instead called countertenors within classical music. Within contemporary music, however, the use of the term "tenor" for these male voices would be more appropriate. Teaching voice within non-classical music is an emerging field. Up to this point, voice teachers and voice research have been largely concentrated with classical methods of singing. However,
Terminology model an object-oriented database schema, is can be transformed without loss of information into an object-oriented database schema. Thus, the terminology model is a method for problem analysis on the one side and a mean of defining database schema on the other side. Several terminology models have been developed and published in the field of statistics: Terminology model A terminology model is a refinement of a concept system. Within a terminology model the concepts (object types) of a specific problem or subject area are defined by subject matter experts in terms of concept (object type) definitions and definitions of subordinated concepts