Not only is the voice the principal means of human communication, but it was undoubtedly the first musical instrument. The principal difference between singing and speaking is that in singing the vowel sounds are sustained and given definite pitch. Despite the innate and natural quality of singing, the training of the singing voice for artistic purposes is among the most subtle and difficult branches of music pedagogy. The instrument is within the performer, and the condition of the vocal apparatus, and thus the quality of the voice, is strictly dependent on the physical and mental condition of the singer. Since the vocal impulse cannot actually be described, the teacher's task is to provide the pupil with concepts, usually systematized into a vocal "method," that will free the vocal apparatus from restrictive tensions and lead ultimately to the complete coordination of all the faculties involved. The foundation of the scientific study of the voice was laid in the middle of the 19th cent. by Manuel Patricio Rodríguez García, a successful voice teacher and writer, who invented the laryngoscope (used to examine the interior of the larynx).
Because of the great changes that have taken place in the art of singing within Western musical culture, modern singers can only approximate the vocal timbre of previous eras. Gregorian chant may have been sung with a nasal timbre resembling Oriental technique. The Neapolitan operatic school developed the virtuoso art of bel canto, in which brilliance of vocal technique was stressed rather than romantic expression or dramatic interpretation. The sound of the castrato (see eunuch), for which many 17th- and 18th-century soprano and alto roles were intended, is approached by several contemporary countertenors using falsetto techniques. The electronic microphone has, in recent times, had an enormous impact on the voice and on styles of singing, through its ability to project very quiet, intimate sounds, and to magnify exciting sounds to a feverish intensity.
Singing voices are classified according to range as soprano and contralto, the high and low female voices, with mezzo-soprano as an intermediate classification; and as tenor and bass, the high and low male voices, with baritone as an intermediate classification. Within these ranges there are specific designations of the quality of a voice, e.g., coloratura soprano. Choral music generally requires a range of about an octave and a half for each voice; a solo singer must have at least two octaves, and some have been known to possess ranges of three, even three and a half, octaves. See also song.
See D. Stevens, ed., A History of Song (1960); R. Luchsinger and G. E. Arnold, Voice, Speech, Language (1965); R. Rushmore, The Singing Voice (1971); S. Butenschon and H. Borchgrevink, Voice and Song (1982).
The term voice-over can also refer to the actual voice actor who performed the recording. The terms voice actor, narrator, voice artist, announcer are all similarly used.
Voice-overs are often used to create the effect of storytelling by a character/omniscient narrator. For example, in The Usual Suspects, the character of Verbal Kint has voice-over segments as he is recounting details of a crime. Other examples of storytelling voice overs can be heard The Shawshank Redemption and Big Fish.
Sometimes, voiceover can be used to aid continuity in edited versions of films, in order for the audience to gain a better understanding of what has gone on between scenes. This was done when the 1948 Joan of Arc , starring Ingrid Bergman, turned out to be far from the box-office and critical hit that was expected, and was edited down from 145 minutes to 100 minutes for its second run in theatres. The edited version, which circulated for years, used narration to conceal the fact that large chunks of the film had been cut. In the full-length version, restored in 1998 and released on DVD in 2004, the voiceover narration is heard only at the beginning of the film.
The genre of film noir is especially associated with the voice-over technique.
In radio, voice-overs are an integral part of the success of the radio programme. Although the announcer holds the prestige and claims all the glory, it is the voice-over artist that is the real drive behind the show. For example, David M. Green's Summer Pow-Wow and his voice-over artist, Tim Wray.
Live sports broadcasts are usually shown as extensive voice-overs by expert announcers over video of the sporting event.
Game shows formerly made extensive use of voice-overs to introduce contestants and describe available or awarded prizes, but this technique has diminished as shows have moved toward predominantly cash prizes.
Voice-over commentary by a leading critic, historian, or by the production personnel themselves is often a prominent feature of the release of feature films or documentaries on DVDs.
In the early years, before effective sound recording and mixing, announcements were produced "live" and at-once in a studio with the entire cast, crew and, usually, orchestra. A corporate sponsor hired a producer, who hired writers and voice actors to perform comedy or drama.
The industry expanded very rapidly with the advent of television in the 1950s and the age of highly produced serial radio shows ended. The ability to record high-quality sound on magnetic tape also created opportunities, as has the proliferation of home computers capable of recording, often using inexpensive (even free) software and a microphone of reasonable quality.