Rhythm is shaped by meter. Composers arrange rhythms so that count one of the meter gives the point of reference of the rhythm. Musicians say that a rhythmic pattern originates with count one, and the rhythmic pattern itself indicates where count 1 falls in the beat. Clap the rhythmic melody of your favorite song again. Tap your foot to the beat. As you clap and tap, can you tell where count 1 is?
Rhythm is generated by divisions of the beat. When music has a steady beat, the rhythmic patterns that comprise the music are generated by sounding tones on the beat, and between the beat. This is accomplished by dividing each beat into groups of 2, 3, 4, 5, 6, 7, 8, and sometimes more, divisions. These divisions are called duplets, triplets, quadruplets, quintuplets, sextuplets, septuplets, and octuplet divisions, respectively. Many music cultures have verbal (mnemonic) counting systems for rhythm, which sound like an abstract language of numbers and percussive syllables. One of the most complex verbal counting systems is found in India. The rhythmic system used in the West is of modest complexity only by comparison to the South Indian system of rhythm
Rhythmic patterns are often repeated. Rhythmic patterns most often undergo a process of repetition in music. Repetition of material is a very important procedure in music, more so than in any other artistic discipline (for example, drama, literature, poetry, dance, painting, sculpture, cinema, or others). Music tends to wander aimlessly if its component material is not repeated. Repetition in music creates a sense of structural continuity and cohesiveness within any given composition. Repetition also allows musical material to assume an abstract sense of "identity", or a sense of musical personality. Of course too much repetition leads to predictability, so the processes of variation or contrast (new material) may be introduced. Repetition, variation, and contrast are the foundational procedures on which music composition rests. These foundational procedures are used in the creation of all the basic elements of music. There is a total number of notes that comprises the rhythms of the melody and harmony in any measure of music. The actual number of notes in a particular measure constitutes the rhythmic saturation of that measure. Greater rhythmic saturation of a measure of music adds more rhythmic energy to that measure, while lesser rhythmic saturation of a measure of music lowers the rhythmic energy of that measure.
Rhythm is articulated by implied dynamic and agogic accents. Musicians seldom play a piece of music exactly the same in repeated performances. Each time a performer plays a piece he/she "interprets" the piece by playing certain notes slightly louder or softer and longer or shorter than during previous performances. The specific manner in which notes are played describes the articulation of those notes. Articulation is one of the interpretive areas of music because the performer plays certain notes slightly differently in length or loudness. Articulation is said to be "interpretive" in music because it imparts spontaneity and animation to rhythm.
The articulation of music notes by length or loudness is accomplished by accent. An accent is defined as an intensification of length or loudness of tones when those tones are compared with surrounding notes. There are two types of accent in music: agogic (length), and dynamic (loudness).
An agogic accent is a stress of length, whereby a certain note is played longer than other notes within the rhythmic pattern. It is very natural to accent the notes that fall on the downbeat of a measure with an agogic accent. This gives the downbeat a "feeling" of greater weight and intensity. Other notes of the measure may be accented agogically to make the rhythms of the passage "come alive".
Playing notes shorter and separating them from each other is called staccato, or staccato articulation. Playing notes longer and connecting them to each other is called legato, or legato articulation. In general, notes are played more staccato in faster tempi, while, for slower tempi, notes are played with more legato articulation.
A dynamic accent is a stress of loudness, whereby a certain note is played louder than other notes within the rhythmic pattern. Again, it is very natural to accent the notes that fall on the downbeat of a measure with a dynamic accent, as this too gives the downbeat a "feeling" of weight and intensity. Other notes of the measure may be accented dynamically to make the rhythms of the passage "come alive". Of course, a downbeat may receive both an agogic and a dynamic accent, but successive repetition of this dual articulation may cause the musical passage to sound awkward.
The performance of music by "interpreted" accent brings an "implied" component to accent, in that such accents are not notated in the music. These accents are interpolated (inserted) into the music by the "interpretation" (free choice) of the performer and therefore are implied accents. Interpolative articulation adds components of spontaneity, changeability, and improvisation to music and makes music that is notated have more "life" during performance.
Rhythm may mask meter through syncopation. A special compositional procedure in music happens when notes occur only between beats and do not occur on beats. This effect "masks" the prevailing meter and the downbeat of the meter is difficult to identify. This compositional procedure is known as syncopation. It is heard in most musics at climax points in rhythmically active passages. Ragtime, Blues, Jazz, Rhythm and Blues, Rock and Roll, and Rap are examples of styles of music that are defined by the use of syncopation.
Syncopated notes usually receive additional "implied" accent by the performer and syncopation imparts a very energizing yet unstable mood to any passage of music.
Rhythm contributes to the effect of motion in music. Rhythm and rhythmic patterns are a direct contributor to the effect of movement (motion) in music. The repetition of a rhythmic pattern creates a sense of forward motion by the appearance of successive sounds in a continuum of real time (sound exists in an environment of actual time from one second to the next). The interplay of different note lengths is perceived as sonic motion by a listener and the forward thrust of this sonic motion is sustained by variation and contrast of the initial rhythmic pattern. If a person speaks a sentence in a foreign language, it is possible to sense the forward momentum, or "motion" of their words even though the meaning of the words is unintelligible. This same effect is achieved in music by the occurrence of rhythmic patterns of musical sound occurringin real time.