MONOCORD. — The m. was the musical instrument to which the most varied applications were given: initially an experimental instrument for acoustics, from the 9th century onward it became a teaching instrument; finally, after the 14th century, under the name of marine trumpet (Trumscheit), it became a bowed instrument used in churches during the 18th century, especially by nuns, whence the name Nonnengeige by which it was known in German-speaking countries.
The m. consists essentially of a string stretched over a soundbox of variable length by means of a bridge. The oral traditions recorded in the writings of Oddone, Ubaldo, Guido, Adelboldo, Bernone, Notker Labeo, Guglielmo di Hirsau, Walter Odington, Joannes de Muris, etc., determined the quality, length, and thickness of the string and soundbox, as well as the various procedures for obtaining divisions of the string capable of producing the various generally diatonic intervals possible within the diagram of an octave and a fifth or of two octaves.
The invention of the m. is attributed to Pythagoras, who is said to have learned of it from the Egyptians. The first treatise to discuss it is that of Euclid (ca. 300 B.C.), under the name of Sectio canonis. Boethius (De institutione Musicae, IV, chaps. 6–12) derives the chromatic and enharmonic intervals from the divisions of the m. Whereas Boethius and Ubaldo used Greek and Latin letters to mark the successive sounds, after Oddone it became customary to mark on the soundbox itself, with the first 7 Latin letters, the various points at which to place the bridge before setting the string vibrating with the finger or a plectrum.
The use of the m. as a pedagogical instrument developed alongside the advancement of musical notation, initially imprecise in many neumes (v. NOTAZIONE), then written on a staff and decipherable without further aid from the teacher’s memory. The proliferation of attempts at alphabetic notation at the end of the 10th century and in the 11th century should be related to the greater ease with which the pupil could find on the m. the alphabetic letter first read on the parchment and thus the desired sound. A treatise, Musica theoretica, falsely attributed to Bede the Venerable (PL 110, 911–20) and recognized as the work of a master Lambert (cf. K. Schlesinger, The Greek Foundations of the Theory of Music, in The Musical Standard, 27 [1926], p. 198 ff.), demonstrates how, in the 13th century, the accuracy of intonation in the polyphony of the Ars nova was checked on the m., since this author explains how to obtain simultaneous consonances on the m.