James of Liege

Jakobus von Lüttich , also Jacobus Leodiensis, Jacobus van Luik and Jacques de Liège (* around 1260, † after 1330) was a Franco-Flemish music theorist . As with many contemporaries, very little is known of his curriculum vitae.

Speculum Musicae

He is the author of the seven-volume work Speculum Musicae . This work was originally attributed to Johannes de Muris . However, this is not tenable, since the first letters of the texts of the seven volumes form the acrostic "IACOBUS" and thus reveal the name of the author. This writing was planned as a pamphlet against the Ars Nova . But this became the most extensive music encyclopedia of the entire Middle Ages.

construction

The speculum is an encyclopedic work. Volumes 1–5 are devoted to theoretical music theory, musica speculativa . In the last two volumes he takes a close look at the performance of the music, the musica practica .

• Volume 1 deals with the fundamentals that are necessary to understand musical consonances. He makes reference to Boëthius , Isidore of Seville , Guido of Arezzo , Aristotle , Plato and Petrus Comestor . The volume ends with a chapter on the harmony theory of Pythagoras .
• Volume 2 deals with consonances on the basis of the monochord . The different intervals are dealt with in separate sections: from chapter 8: diapason (octave), from chapter 23: to diapason (double octave), from chapter 27: diapente (fifth), from chapter 32: diatessaron (fourth), from chapter 38: tone (whole tone)
• Volume 3 is entirely filled with mathematical considerations about proportions and intervals, and their divisions.
• Volume 4 evaluates the consonances, compares them and deals with their progression. Here he is already using the term cadence, which means that more imperfect consonances, according to their nature, progress to more perfect ones. So the second and the minor third progress to unison; the major third to the fifth, the fourth either in unison or the fifth. The fifth is considered stable, the major sixth and the minor seventh progress either to the fifth or to the octave. Minor sixth and major Sept are not mentioned.
• Volume 5 deals with three different types of tetrachords . James' sources for this are Boethius and Guido of Arezzo. The comparison of these tetrachords with the Guidonic hexachords is also discussed here.
• Volume 6 describes the liturgical unanimity ( Gregorian chant ), especially the church modes, but also the notation and the repertoire.
• Volume 7, on the other hand, deals with mensural music. Here he primarily defends the Ars Antiqua, but - contrary to popular opinion - without condemning the Ars Nova . He refuses to allow the semibrevis as a divisible value. He is also bothered by the equality of the imperfect mode. (More on these innovations in the article Mensural Notation ).

literature

• Jacobus of Liège . In: The New Grove Dictionary of Music and Musicians , 2nd edition
• Jacobus of Liege . In: MGG , 2nd edition
• Jan A. Aertsen: Speculum musicae as a mirror of philosophy. In: Music - and the history of philosophy and natural sciences in the Middle Ages , ed. by Frank Hentschel, Cologne 1998, pp. 305–321.