Arezzo closes his Epistola Michaeli Monacho (“Letter to Brother Michael”), advocating recourse to the already-published doctrines of Enchiridion by Abbotado (which probably refers to the French theory cycle Musica enchiriadis), and Boethius’ treatise.’ Guido, in addition to commending his own earlier works, claims that his Epistola, his last work, is essentially a simplification of ideas already in circulation. On the contrary, it includes a remarkable innovation: solmization interpreted through ut, re, mi, fa, sol, lao When Oliver Strunk translated Guido’s procedure, he brought to a wide readership the origin and language of a paradigm for singing, “do-remi,” which has become both facile and ubiquitous. However, Strunk did not translate all of Guido’s Epistola; he left out the portion on the monochord, ” which represents another way of facilitating singing. It is not surprising that Guido’s monochords have made little impression upon scholars and have engendered little separate comment. Perhaps one cannot fully appreciate the intentions of such a renowned theorist as Guido until having dissected and compared the anatomies of the monochords, as we have essayed. Nor can one, I believe, reconstruct these tabletop instruments, either on paper or sounding, without a deep satisfaction, which Guido, or for that matter, Euclid, long before him, must also have felt at the rediscovery of the laws of Nature. One cannot thereby help but be astounded at the simultaneous complexity and simplicity of these laws.