MONOCHORD. - The monochord was for music the instrument that had the most varied applications: at first an experimental instrument for acoustics, it was, from the 9th century onward, a didactic instrument; finally, after the 14th century, under the name of tromba marina (Trumscheit), it became a bowed instrument used in churches during the 18th century, especially by nuns, whence the name Nonnengeige that it had in the Germanic countries.
The monochord consists essentially of a string stretched over a resonance box, of variable length, by means of a bridge. Oral traditions, reported in the writings of Odo, Ubald, Guido, Adelbold, Berno, Notker Labeo, William of Hirsau, Walter Odington, Joannes de Muris, etc., determined the quality, length, and thickness of the string and of the box, and the various procedures for obtaining the divisions of the string such as to produce the various intervals, generally diatonic, possible within the diagram of an octave and a fifth or two octaves.
The invention of the monochord is attributed to Pythagoras, who would have learned of it from the Egyptians. The first treatise that speaks of it is that of Euclid (ca. 300 B.C.) under the name Sectio canonis. Boethius (De institutione Musicae, IV, chaps. 6-12) derives the chromatic and enharmonic intervals from the divisions of the monochord. While Boethius and Ubald use Greek and Latin letters to mark the successive sounds, after Odo it became customary to mark on the box itself, with the first 7 Latin letters, the various points where the bridge was to be placed before imparting vibrations to the string with the finger or with a plectrum.
The use of the monochord as a pedagogical instrument developed with the progress of musical notation, at first imprecise in many neumes (v. NOTAZIONE), then written on a staff and decipherable without further help from the teacher's memory. The multiplication of attempts at alphabetic notation at the end of the 10th century and in the 11th century must be connected with the greater ease for the pupil of finding on the monochord the alphabetic letter read first on the parchment and thus the desired sound. A treatise, Musica theoretica, falsely attributed to the Venerable Bede (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 intonations in the polyphony of the Ars nova was checked on the monochord, since this author explains how to obtain simultaneous consonances on the monochord.
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Pietro Thomas