The Hexachord System

Guido's six syllables turned pitch into a movable ladder, letting singers solmize without an instrument.

Related

MedievalModeInterval

Six syllables changed no pitch, yet they let a singer find notes without an instrument. Guido put the tool in a short treatise, and European solmization acquired a shared ruler.

Time and place

Italy, late 1020s. Guido taught singing at the monastery of Pomposa and later directed the cathedral school at Arezzo. His Micrologus was written around 1025 to 1030; the exact year is disputed, so scholars usually say only the eleventh century.

What happened

Guido took the opening note of each line of the hymn Ut queant laxis and drew six syllables from them, ut, re, mi, fa, sol, la. The six notes form a hexachord with the semitone fixed between mi and fa. The system sat in three positions, on G, C and F, called the hard, natural and soft hexachords. At the edges the singer had to mutate, renaming the same pitch in order to move into the next hexachord. The whole available range, from the low Gamma to the high la, was the gamut. Solmization named relative position rather than absolute pitch, so one melody could be sung on the same syllables at different heights. The system lasted into the seventeenth century, when seven-note solmization replaced it.

What changed

Reading music no longer required an instrument. Cathedral schools could teach singing with a common vocabulary, and pitches on the four-line staff had names that could be spoken. Mutation forced singers to think in intervals rather than memorised tunes. The limits were real, since the tritone between fa and mi had to be avoided, and a B had to be assigned to the hard or the soft hexachord, a decision that grew into musica ficta. The idea of movable solmization survived, and both movable do and the Kodaly method trace back to this step.

Listen for the turn

Begin with the organ verset on Ut queant laxis, where each phrase starts one step higher, the line from which the syllables were taken. Then the hymn Pange lingua, which moves mostly by step and needs little mutation, the comfortable range of the system. Finally Hildegard's O Virtus Sapientiae, whose range exceeds a sixth, so a singer must mutate back and forth to bring high and low into one set of syllables. All three sit inside the system; what differs is how often the singer changes hexachord.

Related

This turn belongs to Medieval; see Mode and Interval.

Sources

• Grove Music Online, entry Hexachord — dates and terminology checked, not quoted
• The New Grove Dictionary of Music and Musicians, 2nd ed., entry Guido of Arezzo — biography checked, not quoted

Used for fact-checking only; all prose is original.