Musicology Annotation << Back On diminished triads, the ambivalence of the pitch-letter B and the musical theory of Nikolay Diletsky regarding four-part choral settings of the Znamenny Chant Semenenok Ivliy A. The article elaborates on characteristic features of four-part choral settings of the Znamenny Chant of the last quarter of the 17th century and the first half of the 18th century, such as: diminished triads in conjunct ascending & descending chord movement, cross-relations of B-natural vs B-fl at modal function in chord progressions. These special aspects are explained from the viewpoint of the 17th-century modal theory (the hexachord system, etc.). The authority of the Nikolay Diletsky’s “Idea of Musical Grammar” treatise is questioned as a guide to clarification of the mentioned issues. Keywords: Znamenny Chant, Partes (choral) settings, diminished triads, cross-relation, hexachord system, modal theory, Obikhod scale, clavis (modal pitch-letter), vox (hexachordal syllable-name), hexachord locus (degree or place in the gamut), treatise, Nikolay Diletsky, 1675–1750. DOI: 10.25791/musicology.06.2019.685 Contacts: - Pp. 19-28.