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I had to look it up. A counter-tenor (also contra tenor) is a type of classical male singing voice whose vocal range is equivalent to that of the female contralto or mezzo-soprano voice types, generally extending from around G3 to D5 or E5, although a sopranist (a specific kind of countertenor) may match the soprano's range of around C4 to C6. Countertenors often are baritones or tenors at core, but rarely use this vocal range in performance. The nature of the counter-tenor voice has radically changed throughout musical history, from a modal voice, to a modal and falsetto voice, to the primarily falsetto voice which is denoted by the term today. This is partly because of changes in human physiology, and partly because of fluctuations in pitch.