Analysis of information sources in references of the Wikipedia article "Part (music)" in English language version.
One frequently distinguishes the outer (highest and lowest) parts (Ger. Aussensatz) from the inner (middle) part or parts.
In early polyphony parts were named not according to vocal range or timbre, but on the basis of their function in the contrapuntal design [...] With the introduction of such names as 'contratenor bassus', part names began to take on registral connotations.
The primary division of certain large-scale works (especially oratorios), equivalent to the act in theatrical works.
In certain large-scale genres, e.g. oratorios, 'Part' is used to designate the main division of the work.
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