Singing is the act of producing musical sounds with the voice, and augments regular speech by the use of both tonality and rhythm. One who sings is called a singer or vocalist. Singers perform music (arias, recitatives, songs etc.) that can be sung either with or without accompaniment by musical instruments. Singing is often done in a group of other musicians, such as in a choir of singers with different voice ranges, or in an ensemble with instrumentalists, such as an orchestra or as a soloist.
In many respects human song is a form of sustained speech. Singing can be formal or informal, arranged or improvised. It may be done for pleasure, comfort, ritual, education, or profit. Excellence in singing may require time, dedication, instruction, and regular practice. They typically take voice training provided by voice teachers or vocal coaches throughout their careers.
Composers who write vocal music must have an understanding of the skills, talents, and vocal properties of singers. Voice classification is the process by which human singing voices are evaluated and are thereby designated into voice types. These qualities include but are not limited to: vocal range, vocal weight, vocal tessitura, vocal timbre and vocal transition points such as breaks and lifts within the voice. Voice classification is often used within opera to associate possible roles with potential voices. Women are typically divided into four groups: coloratura, soprano, mezzo-soprano and contralto. Men are usually divided into four groups: counter-tenor, tenor, baritone and bass. Within each of these major categories there are several sub-categories that identify specific vocal qualities like coloratura facility and vocal weight to differentiate between voices.
