The vocal ensemble without instruments is called A cappella.

A cappella (a cappella) refers to a multi-part musical performance that uses only the human voice without instrumental accompaniment, and also includes vocal music written for this purpose. A cappella singing can give full play to the expressive power of different voices, voice areas, and timbres of men and women, and maintain the overall coordination of sound quality and unity of style.

A cappella (A cappella) Italian original meaning is church style, which refers to polyphonic (multi-part) music sung by unaccompanied voices. Originally used in religious choral music, it is now also used in secular music.

It is a unique form of expression in the art of choral music. What distinguishes it from other types of chorus is that it is not combined with any musical instruments and only uses the human voice as a tool of expression.

Contemporary a cappella chorus is most different from traditional chorus in the following two points:

Onomatopoeia technique: that is, the singer uses his voice to imitate various sounds (especially musical instruments), Among them, imitation of percussion instruments is the most common. Some singers are also good at imitating the timbres of wind instruments, electric guitars and even other musical instruments. With the help of audio technology, the sounds imitated by human voices are often almost realistic.

Non-meaning syllables: syllables that have no actual meaning, such as falala. Traditional choruses sometimes contain non-verbal syllables. For example, English pastoral songs often include falala passages, but the proportion is much smaller than that of contemporary repertoire. The prelude, interlude, ending and accompaniment parts of general songs are often sung with non-substantial syllables; there are also some pure music in which all parts sing non-substantial syllables.