Organum: a second voice composed to decorate an original plainchant

The early polyphony that we call organum was probably improvised before it was written down. Motion in parallel intervals and heterophony appear in many musical cultures and were probably practiced in Europe. 

Polyphony was described in Musica enchiriadis and Scholica enchiriadis, a treatise and a textbook from ca. 900. In this early organum, an added voice (organal voice or vox organalis) appears below a chant melody (principal voice or voix principalis), moving either in parallel motion at the interval of a fourth or fifth (parallel organum) or in a mix of parallel and oblique motion (organum with oblique motion). 
--A History of Western Music, fifth edition, by Grout/Palisca

Polyphonic settings of Latin poems called versus are the earliest polyphony not based on chant. Manuscripts for these types of polyphony use score notation (one part above the other, with notes that sound together aligned vertically), but do not indicate rhythm.

Organum now usually refers to polyphony used in liturgical music from the late 9th century to c. 1250. Originally, it was a neumatic and melismatic chant section by the choir at the beginning and end of a piece. 
The number of voices contained in a section of organum determines its nomenclature (ie: 2 voices is Organum duplum, three is Organum triplum four is Organum quadruplum etc).

Several types of organum that developed the high middle ages:

  • Parallel Organum – Strict homophony with parallel 4ths, 5ths, and 8vas. It is syllabic, meaning there is only one note per syllable.
  • Modified Parallel Organum – Each phrase begins in unison, spreads to parallel 4ths and contracts again to unison. It is syllabic.
  • Free Organum – A style of note against note. It is not melismatic between the two voices, but it is melismatic between the text and music of each individual voice. The phrases end on a unison or 8va, and the voices are independent within phrases. In free organum, the added voice usually sings above the chant, although the voices may cross.
  • Florid Organum - A style where the chant is sustained in long notes in the lower voice (called the tenor), while the upper voice sings from one to many notes above each note of the tenor. This style was called organum, organum duplum (double organum), or organum purum (pure organum). 

From florid organum, polyphonic music progressed to what was known as Notre Dame organum.

Notre Dame Organum.

Notre Dame organum originated, as its name suggests, in Notre Dame cathedral in Paris in the late eleventh or early twelfth century and continued to be written there until the fourteenth century.. The musicians at the Notre Dame school were the first to work out how to notate more than two voices by fixing a definite rhythm. The style spread across western Europe.

The most famous (and probably best) composers of organum were Leonin, composer of Magnus Liber Organi (including Graduals and Alleluias he had improved upon), and Perotin, who modified and improved on Leonin's work by adding better clausulae. These men were the first organum composers identified by name.

Leonin was born in about 1135 CE. His compositions were based on the Gregorian chants. The original chant served as the foundation and a second voice (the descant), was added to the original chant. 

Perotin (Perotinus) was one of Leonin's students and appears to have been born between 1155 and 1160. During his studies with Leonin, he made some important revisions to Leonin's Magnus Liber Organi and developed some ideas of his own about polyphony. To the additional voice part that Leonin added, Perotin added a third and fourth vocal part  Perotin named the three additional parts the duplum, triplum, and quadruplum. All three of these voice parts were based on and written above the original chant.

There are three types of Notre Dame Organum:

  • Organum purum
    The most simple organum. It has no rhythm and consists of a tenor voice, which sings the original plainchant and a duplum.
  • Copula.
    Still a very simple organum. The top voice or voices in this case do have rhythm, but the original chant is still without any meter
  • Discant
    The most advanced form of Notre Dame organum. Both the chant and the organal voices have rhythm. Although the original setting of the chant was not rhythmic, composers maintained its integrity by using the same pitches in the same order, often repeating the pitc hes for one syllable or word over and over.

From the thirteenth century, the use of organum in liturgical music declined sharply.

Or"ga*non (?), Or"ga*num (?), n. [NL. organon, L. organum. See Organ.]

An organ or instrument; hence, a method by which philosophical or scientific investigation may be conducted; -- a term adopted from the Aristotelian writers by Lord Bacon, as the title ("Novum Organon") of part of his treatise on philosophical method.

Sir. W. Hamilton.


© Webster 1913.

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