The word is also used as equivalent to the soprano voice, the highest pitch or range of the human voice, but is generally confined to a boy's voice of this quality, "soprano" being used for the corresponding female voice.
The origin of the application of the term treble, a doublet of "triple" or "threefold" (from Latin triplus, "triple"; cf. "double" from duplus), to the highest voice or part comes from early plainsong. The chief melody was given to the tenor, the second part to the alto (discantus, or contralto), and where a third part (triplum) was added, it was assigned to the highest voice, the soprano or treble.
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