Western music theory is based on the following rules and concepts to describe rhythm (except for a few exceptions which I won’t discuss in this article) :
- Elements composing a musical piece are rhythmically defined by their time position and duration.
- Time is considered linear and a graduation system is used to measure and describe rhythm. The graduation divides time into units which in turn are subdivided into sub-units. The graduation is made in base 2: units are divided into two sub-units, divided in turn into two sub-sub-units and so on : halves (2), crochets (4), quavers (8), semi-quavers (16), etc.
- Units are commonly called beats and their frequency defines the pulse or tempo of the music, expressed in beats per minute. Sub-units represent the micropulse or microtime. Because a microtime is an integer division of the unit, its frequency is a harmonic of the pulse.
- Beats are grouped into longer periods (sub‑harmonics) called bars. The bar-level is typically the only one that can afford other ratios than 2-exponents. The harmonic system that comprises the frequencies of the bar, the pulse and its subdivisions is called the meter.
- Micropulse frequencies that are not a 2-exponent of the pulse are exceptions and are called tuplets. They are expressed as a ratio towards another « regular », 2‑exponent micropulse (for example, the triplet, expressed in relation to the quaver).
This Western metric system has now been used for centuries by music scholars to analyze, describe, study and teach music. It was also used as a reference to analyze music cultures and traditions other than its own.
However in my opinion this metric system fails to describe accurately the rhythm phenomena occurring when musicians play, especially when it comes to polyrhythmical music such as African or Afro-rooted traditional music. This I think, is due to two major problems/misconceptions :
- The Western metric system is a limited harmonic system, as there is always only one single level of subdivision : the pulse is divided into a single number of sub‑divisions, which in turn are singly sub-divided and so on. Never does it allow the coexistence of different divisions. Although having the possibility of tuplets, the meter is « monophonic » or « biphonic » at most: the bar cycle plus one harmonic (the pulse division of the bar) with its octaves (2-exponent sub-divisions). This means that the meter does not, in essence, consider multiple harmonics of a fundamental frequency happening simultaneously. Instead, when facing music presenting multiple simultaneous divisions and because of its concept of musical time as a single grid of regular graduation, the metric system will attempt to reach for a common multiple of the frequencies in presence.
For example, during my musicology studies I came across an ethnomusicology paper proposing that some African percussionist was playing with 1/100th of beat precision. This is nonsense to me, as it doesn’t describe the actual neuro‑cognitive process at work in the musician.
- Such a normalized metric system is unable to describe the phrasing that some musicians/cultures apply to their microtime. A microtime is termed phrased when some distorsion or swing is applied to the micropulsatory grid resulting into the feeling that the pulse is divided into uneven micropulses. Known examples of this are the swinging eight-note of course, but also the so-called brazilian-sixteenth, ore the recently popularized Gnawa triplets and sixteenth. I reckon that musical time is cyclic and that the playing musician does not perceive it as being linear. For him/her rather, time flows in waves. One could describe these waves as a cyclic time distorsion with successions of time compression and expansion moments.