The term soprano is one of many vocal range classifications; it refers to the highest of all vocal ranges. To be considered a soprano, a vocalist's range must fall from middle C to a thirteenth above it -- though many soprano singers have ranges the extend far above that. It's generally a category reserved for females, though some males singing in a falsetto can be called soprano. Soprano singing is sometimes considered to be the most difficult and impressive type; whether or not that's actually true, the vocal quality found in a soprano is unlike that of any other classification.
Soprano vocal ranges can be further divided into several different categories. The specificity of these soprano categories is based entirely on the type of music being sung. In typical choral ensembles, a limited number of soprano categories is used; in fact, many choral ensembles will only use one, labeled simply as soprano. But in some cases, where vocal parts require further harmony, choral arrangements will utilize two categories: soprano I and soprano II. Soprano I is the basic soprano part, the part that would be present as simply soprano in a choral ensemble with just one part. Soprano II, also known as mezzo-soprano, is a bit lower than Soprano I, falling somewhere between an alto and a soprano.
Opera, however, is an entirely different ball game where soprano singers are concerned. Operas often contain no less than five soprano parts, all working on the subtle differences between vocal ranges. The highest of these categories is the dramatic soprano, or lead soprano, which is the voice that is typically associated with traditional opera. It's a type of soprano with an incredibly flexible range, one that extends far above the common soprano voice; for this reason, dramatic soprano singers are usually given the lead roles in operas. This type of soprano is so astronomical in range that it, supposedly, can break glass on the best of days; myth or not, that story clearly illustrates the sheer vocal abilities of a dramatic soprano, abilities that take years to hone.
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