|Pythagoras in School of Athens|
A monochord is an ancient musical and scientific laboratory instrument. It is also the class-name for any musical stringed instrument having only one string (such as the Vietnamese Đàn bầu). The word “monochord” comes from the Greek and means literally “one string.” In a true monochord, a single string is stretched over a sound box. The string is fixed at both ends while one or many movable bridges are manipulated to demonstrate mathematical relationships between sounds.
[Slide 3-3: Closeup of Tablet, Bouleau. Janson, H. W. History of Art. (Fifth Edition.NY: Abrams, 1995). p.497
Raphael’s School of Athens shows Pythagoras is explaining the musical ratios to a pupil. Notice the tablet. It shows the words diatessaron, diapente, diapason. The roman numerals for 6, 8, 9, and 12, showing the ratio of the intervals, same as in the music book frontispiece.The word for the tone, ΕΠΟΓΛΟΩΝΕΠΟΓΛΟΩΝΕΠΟΓΛΟΩΝΕΠΟΓΛΟΩΝ, at the top. Under the tablet is a triangular number 10 called the sacred tetractys]
The monochord can be used to illustrate the mathematical properties of musical pitch. For example, when a monochord’s string is open it vibrates at a particular frequency and produces a pitch. When the length of the string is halved, and plucked, it produces a pitch an octave higher and the string vibrates at twice the frequency of the original (2:1) Play (help·info). Half of this length will produce a pitch two octaves higher than the original—four times the initial frequency (4:1)—and so on. Standard diatonic Pythagorean tuning (Ptolemy’s Diatonic Ditonic) is easily derived starting from superparticular ratios, (n+1)/n, constructed from the first four counting numbers, the tetractys, measured out on a monochord.
|The Divine Monochord, from Fludd’s Utriusque Cosmi Maioris Scilicet et Minoris Metaphysica (1617)|
The name “monochord” is sometimes incorrectly applied to an instrument with one open string and a second string with a movable bridge; however, such a two-string instrument is properly called a bichord. With two strings you can easily demonstrate how various musical intervals sound. Both open strings are tuned to the same pitch, and then the movable bridge is put in a mathematical position to demonstrate, for instance, the major third (at 4/5th of the string length) Play (help·info) or the minor third (at 5/6th of the string length) Play (help·info).
See: Atalanta fugiens