Vocal music is singing performed either solo or with multiple singers, without instrumental accompaniment (a cappella), or with accompaniment if the singing is the main focus. Music that contains singing but does not feature it prominently is generally considered to be instrumental music.
Vocal music usually has sung words called lyrics, although there are many examples of vocal music that is performed without words, instead using non-linguistic syllables or other sounds. A short piece of vocal music with lyrics is broadly termed a song, and it is additionally called an aria in opera and other classical music and a hymn in religious music.