found: New Grove dict. of mus. online, July 10, 2002:under Dialogue (As applied to music, used in two general senses: to denote the setting of a text involving conversational exchanges between two or more characters; and to describe a musical work (or part of a work) that uses devices such as alternation, echo or contrast in a way that seems analogous to spoken dialogue; in the second sense "dialogue" has been used as a title for certain instrumental works (particularly for organ) that exploit contrasts in tone colour; used in its first sense, is now most frequently encountered in connection with the dialogue of opera and other stage works; during the 16th and 17th centuries also used more specifically to denote the independent dialogue settings included in collections of madrigals, motets and cantatas)
