Formerly it was thought he was from Lorraine or Flanders, based on a dedication he made in his treatise, but other more recent evidence suggests that he may have been a John Cotton from England who worked under an abbot named Fulgentius at or near St. Gallen (in modern Switzerland).
Unlike many medieval treatises, it largely avoids metaphysical speculations, instead functioning as a practical guide for a working musician.
Most of his examples are note-against-note, and demonstrate how to end on a fifth or an octave by good voice-leading; he emphasizes the importance of contrary motion, a practice which differed from the parallel organum of the preceding centuries (though it probably reflected a current practice; in the absence of many surviving 11th-century manuscripts it is difficult to date when the switch from mostly parallel to mostly contrary motion occurred).
His directions for composing melody, with their careful and practical instructions involving pacing, position of high and low notes, and use of recognizable figurations at different pitch levels seem to imply that he may have had some experience himself.
One theory attributes the work to Pope John XXII, but this rests on the very slight foundation that the author styles himself "Joannes servus servorum Dei."
Another theory ascribes it to a certain "Joannes Scolasticus", a monk of St. Matthias' Abbey at Trier, all that is known of whom is that he was living about 1047, and that he wrote much music, but there seems to be no reason why the work should not have been written by the unknown Englishman, John Cotton.