Singing solely or mainly without instrumental accompaniment.
Related to a form of purely vocal music mostly associated with American college performance groups.
A vocal performance with no instrumental accompaniment.
In a manner of a choir with no instrumental accompaniment; literally, "in the style of the (Sistine) Chapel (in Rome)", such as a musical Mass done a cappella.
Without companions; solitary.
Unfrequented by people; desolate.
Unhappy because of feeling isolated from contact with other people.