Musica enchiriadis

It is the first surviving attempt to set up a system of rules for polyphony in western art music.

[3] This music theory treatise, along with its companion text, Scolica enchiriadis, was widely circulated in medieval manuscripts, often in association with Boethius' De institutione musica.

The author here shows how consonant intervals should be used to compose or improvise the type of early-medieval polyphonic music called [4] organum, an early style of note-against-note polyphony; several examples of which are included in the treatise.

[4] (Scolica enchiriadis also observes that some melodies should be sung "more quickly" (celerius), others "more slowly" (morosius).)

A critical edition of the treatises was published in 1981, and an English translation by Raymond Erickson in 1995.

The notation used in Musica enchiriadis. The scale comprises four tetrachords. The symbols indicating the notes are rotated and mirrored depending on the tetrachords. A modern transcription of the notes is below.