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Although some women who sing alto in a choir are contraltos, many would be more accurately called mezzo-sopranos (a voice of somewhat higher range and different timbre). Men singing in this range are countertenors, although this term is a source of considerable controversy,[citation needed] some authorities preferring the usage of the term "male alto" for those countertenors who use a predominantly falsetto voice production (boys singing in their natural range may be termed "boy altos"[2]).