Third Notation: Short Measures with Rhythmic Signs

Definition: Dividing music into short measures with equal or unequal beats, using special rhythmic signs placed above beats to indicate exact durations, creating a hybrid system combining metric framework with precise durational notation.

Messiaen's Treatment: When performers play the same rhythms and these rhythms do not gather into normal meters, it is necessary to divide the music into short measures. A numeral written at the head of each measure indicates the number of beats in it. These beats are equal or unequal in duration; it is necessary then to have recourse to some rhythmic signs placed above the beats to indicate their exact duration.

In the orchestral version of Poèmes pour Mi, upon advice of Roger Désormière (orchestra conductor and inventor of these signs), Messiaen used specific rhythmic signs (Example 63) and their doublings (Example 64), with which one can notate the most difficult rhythms.

This notation necessitates preliminary agreement between musicians and conductor and a rather forbidding effort at first reading. The thing is nevertheless very possible.

Modern Context: This represents an innovative hybrid notation attempting to bridge metric and ametric organization. The system creates:

• Flexible beat lengths: Each measure contains a specified number of beats, but beat durations vary according to the signs
• Visual clarity: Signs above the staff provide quick visual reference for beat durations
• Conductor coordination: The conductor can show beat patterns while signs specify exact durations

This anticipates later notational innovations:

• Time-unit box notation: Systems where boxes contain specified durations (Cage, Feldman)
• Metric modulation notation: Carter's use of changing tempo relationships indicated through proportional relationships
• Contemporary conductor's scores: Specialized notations designed for conductor reference separate from performer parts

The requirement for preliminary agreement between musicians and conductor acknowledges that this notation requires ensemble training—performers must learn the system before applying it. The initial difficulty suggests this notation serves specialized contexts (contemporary music ensembles, performances with extended rehearsal time) rather than general use.

Examples: Examples 63–64 demonstrate the rhythmic signs and their doublings.