Posts In: rhythm

Rhythmic Shells

January 14, 2010 General News, Ideas 1 Comment

With the contour grammar engine in development, I am still searching for ways to simplify and optimize grammatical representations. At the moment, the most restrictive element of the engine is the separation between rhythm and pitch. In current engines, the two are completely separated into different streams driven by different grammar sets. Not only does this approach render it difficult to work with both streams at the same time, but it also negatively impacts the ability of the engine to produce coherence between pitch and rhythm.

A new idea I call "rhythmic shells," however, might promise an enormous simplification of the process, combining both streams into one while offering greatly improved coherence potential at the same time. The method focuses on stripping pitch words of all length dependency and transforming rhythm into a specification of pitch words. In essence, a rhythmic "shell" is selected, which contains a prescribed number of "slots," each with a distinct duration, and the slots are then filled with pitch words. The method requires that pitch words be functions rather than definitions - that is, they must be of arbitrary length and cannot be precomputed.

Here's a simple diagram of the method:

The shell stream can be specified with a simple data structure like this:


The number on the left side indicates the index of the pitch shell to be used, while the comma-delimited numbers indicate the indices of the pitch functions with which to fill each shell slot. Notice that the phrase produced by a shell can be variated by leaving one or more elements intact while changing the others, creating a different, but still somewhat similar phrase. This will certainly guarantee more coherence.

It is worth noting that, given the functional nature of the pitch words in this description, the method of rhythmic shells if very much like a generalized method of curve-splicing, which was discussed several weeks ago!

In the next few days I put a great deal of work into the contour grammar engine to try to implement the method of rhythmic shells. I also hope to continue finding new innovations for the simplification, unification, and overall improvement of grammar techniques.

Rhythm and Meter

As the foundations upon which music is built, rhythm and meter will play an obvious and pivotal role in my program. Unfortunately, I have read very little on the topics, as Music, the Brain, and Ecstasy devoted only a single chapter to the subject in general. I need to delve deeper into the topic. To do so, I'll need some good sources.

Here are some books I'm looking at:

The first one looks extremely comprehensive and helpful.

Coordination Module

April 2, 2009 Ideas 0 Comments

As I have continued to work on generative plugins and attempted to reverse-engineer familiar music, I have found something lacking in my Core Modules group. I need more than just a structure and progression module - I need a meter/rhythmic module. Such a module would generate information concerning where the strongest beats of each measure lie, how melody should interact with harmony, - with room for syncopation and counterpoint - and more for each segment of a composition.

Although such a module wouldn't make much difference in the case of a standard 4/4 beat, where beats 1, 5, 9, and 13 are heavily accented, it would shine through when unusual rhythmic and metric patterns occured. Almost any metric pattern can sound good if used consistently and coherently. This new module would allow the drum plugin to make sure it hits the accented beats harder - and choose its base beat accordingly, as well as enable the melody to follow a predictable metric pattern.

In short, I need a coordination module.

Now the real question: what rules govern the metric and rhythmic patterns of compositions?

Music, the Brain, and Ecstasy (5)

Music, the Brain, and Ecstasy (Robert Jourdain)
Chapter 5: Rhythm

  • Meter vs. Phrasing
  • Phrasing is a higher-level unit 0f perception than meter, and encompasses harmonic tension, contour, and dynamics
  • Pulse lies at the core of meter
  • Perception of meter is based on prime numbers
  • Polyrhythms are made by playing more than one meter at a time
  • Syncopation is created when beats are accentuated apart from the regular metrical pattern; often the offbeats are regular enough to anticipate
  • Memory vs. Anticipation
  • Memory recalls what has already happened, anticipation draws on memory to predict notes to come (usually only a beat or two in the future)
  • Importance of tempo: if music moves too slowly, the relations are not close enough to be intelligible; if music moves too quickly, the brain cannot keep up with the relation modeling and has to move to shallower relations, missing the nuances of the piece
  • Music needs some gradual changes in tempo; sounds unnatural without them
  • Harmonic complexity vs. Metrical Complexity have an inverse relationship
  • Most listeners and composers alike now opt for harmonic complexity since harmony information is parallel, while metric information is serial, thus more harmony information can be modeled in a shorter time
  • "Memory is music's canvas"
  • "In music, it is phrasing that reaches farthest across time to encompass the deepest relations"
  • "Composers gain maximum effect by interweaving the tensions created by music's various aspects"
  • "Tempo matters because the mechanics of music perception are exceedingly sensitive to the rate at which musical structures are presented to the brain"
  • "Most tempo fluctuations are made intentionally. Music just doesn't sound right without them"
  • "The more harmony wanders from its tonal center, the more it requires rhythmic buttressing"