dubious reliability, Jean d’Outremeuse, alleged that Isabella was the one who told her
father about the adultery of her sisters-in-law.
In 1321, a refusal to admit her to Leeds castle led to a new round of warfare between
Edward II and his uncle Thomas of Lancaster, leading to Thomas’s execution in March
- In September 1324, war broke out with her brother Charles IV of France, and
Isabella was sent to negotiate (March 1325), followed by her son, the future Edward III,
who did homage to Charles for Aquitaine and Ponthieu (September 14).
Isabella then formed a liaison with the exiled English rebel Roger Mortimer, refused
to return to England, and traveled to Hainaut, where the young Edward was betrothed to
the count’s daughter, Philippa, whose dowry was used to hire mercenaries. Isabella and
Mortimer invaded England on September 24, 1326, and the barons rose in favor of her
son. Edward II was captured on November 16 and abdicated on January 20, 1327. In
September, he was murdered in prison.
Isabella and Mortimer, made earl of March in September 1328, ruled England, making
disadvantageous treaties with France (March 1327) and Scotland (May 1328), but on the
night of October 18–19, 1330, the young Edward III seized power in a coup. He had
Mortimer executed on November 29. Isabella no longer played a major role, although she
regained Ponthieu and Montreuil in 1332 and was suggested as a mediator with France in - She died at Hertford on August 23, 1358.
R.Thomas McDonald
[See also: EDWARD II; PHILIP IV THE FAIR; SAINT-SARDOS]
Blackley, F.D., and G.Hermanson. The Household Book of Queen Isabella of England. Edmonton:
University of Alberta Press, 1971.
Hutchinson, H.F. Edward II. New York: Stein and Day, 1972.
ISORHYTHMIC MOTET
. A 20th-century term applied to over 200 works of the 14th and early 15th centuries,
characterized by a repeating pattern of rhythms (the talea) applied to the tenor. The tenor
melody (color) is usually a cantus firmus borrowed from Gregorian chant. Above it, the
phrase structure of motetus and triplum voices recurs at the same point above each talea
statement. A clear hierarchy of rhythms differentiates the voices: the tenor (and
contratenor, a fourth voice common by the mid-14th c.) moves at a slow rate, while
triplum and motetus move quickly, exploiting rhythmic contrasts allowed by the Ars
Nova notational system. The recurring nature of the form is emphasized through hocket,
rhythmic sequences, changes in mensuration, or regular changes in texture.
The earliest examples appear as musical interpolations to a lavish copy of the Livres
de Fauvel (second decade of the 14th c.). A unipartite plan, with constant rhythmic
values in the tenor talea, is the most common formal disposition in the earliest works. By
the second quarter of the century, bipartite motets with diminution were also cultivated,
in which rhythmic values of the tenor talea are halved for a second section. Later in the
century, isorhythmic motets were commonly written in several sections, with rhythmic
values diminishing in a numerical ratio, such as 9:4:3:2 (Portio nature/Ida capillorum by
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