Lacking instrumental accompaniment.

Of, relating to, or characteristic of madrigals; consisting of or dealing with madrigals.

Having the features or characteristics of a madrigal.

Of, pertaining to, or characteristic of a torch song or torch singer. colloquial (originally and chiefly U.S.).

Of a song, recording, etc.: to which one can sing along in accompaniment. Of or characterized by this unsophisticated but cheerful style.