This is what we found on Wikipedia regarding the Brisbane Sings:

Vocal music is a type of singing performed by one or more singers, either with instrumental accompaniment or without instrumental accompaniment (a cappella), in which singing provides the main focus of the piece. Music which employs singing but does not feature it prominently is generally considered to be instrumental music (e.g. the wordless women's choir in the final movement of Holst's symphonic work The Planets) as is music without singing. Music without any non-vocal instrumental accompaniment is referred to as a cappella.

Vocal music typically features sung words called lyrics, although there are notable examples of vocal music that are performed using non-linguistic syllables, sounds, or noises, sometimes as musical onomatopoeia, such as jazz scat singing. A short piece of vocal music with lyrics is broadly termed a song, although in different styles of music, it may be called an aria or hymn.

Vocal music often has a sequence of sustained pitches that rise and fall, creating a melody, but some vocal styles use less distinct pitches, such as chants or a rhythmic speech-like delivery, such as rapping. As well, there are extended vocal techniques that may be used, such as screaming, growling, throat singing, or yodelling. Vocal music is probably the oldest form of music, since it does not require any instrument besides the human voice. All musical cultures have some variation of vocal music.