Vocal music is any type of music in which the tones produced by the human voice are the focal point of the piece. There are many types of vocal music that further divide such pieces into more specific categories.
A capella (Italian for "chapel" or "choir") vocal music is sung without any instrumental accompaniment. Common examples of a capella music include Gregorian chant and some religious prayer music.
The most common type of vocal music is the song. A song is typically composed of a single voice and an accompaniment. An example of this type of vocal music is Franz Schubert's "Schwanengesang," composed in 1828.
Sacred vocal music is music performed in a religious setting or composed for a religious purpose. Examples of this type of vocal music include hymns and Georg Frederic Handel's "The Messiah," composed in 1741.
Secular vocal music is vocal music written for a non-religious setting. Popular vocal music of the Renaissance and Baroque periods were considered to be secular vocal works.
Operas and musicals fall into another type of vocal music called dramatic vocal music. George Gershwin's "Porgy and Bess" and Mozart's "The Magic Flute" are both examples of this vocal music type.