Sunday, June 28, 2020

Rhythmic music - 1 - Organisation and structure

Various basic aspects of rhythm, its patterns and structures in different musical styles of the world.

This is the first of a 2 part post on rhythm in music, please see the second part here


I am interested in music and dance in general, and while enjoying various styles of these, I also find basic similarities between them to be very beautiful. I will also share some things that I personally like and find interesting in certain styles of music, and discuss my aesthetic preferences in general.



Rhythm and beats

Rhythm is a very central concept to music in general. All music (and dance) has two aspects - one of time, and one of form. As a concept, rhythm, which is the aspect of time, is basically independent of the form of music, and is essential because of movement in music, which makes time most important in music. Much of music moves with a regular reference to time. 

The repetitive counting or measuring of time with respect to which this music is measured gives a framework to musical time, and this is measured in time units of fixed length, called beats. These beats or pulses are regular and repeating once decided and the length of any musical sound can be described in relation to them. If the beat in a musical piece has been fixed to be 2 seconds long, every 2 seconds, a beat will happen in time, and the time passed between each successive pair of beats will be 2 seconds. When we use beats to measure musical sounds, a sound that is one beat long will sound twice fast as a sound that is two beats long, for example. 

Musical speed or tempo

The overall speed of music depends on the fixed length of beats in a piece of music, and this musical speed is called tempo. If the beats are long, they will move slowly, and give a slow tempo, if faster, a medium tempo, and shorter, quicker beats will give a fast tempo.  Therefore, a musical piece with a fixed beat of 4 seconds' length, will move twice as slow as a piece which has a fixed beat length of 2 seconds. 

Musical speed or tempo can thus be divided into slow, medium and fast ranges, and depending on the musical style, can be further subdivided into slower and faster variations of each. That is, tempos can be defined broadly over a wide range of speeds for each of the categories, slow, medium and fast, or more narrowly, for smaller, more specified ranges assigned to many variations, or subcategories, of slow, medium and fast tempossuch as very slow, moderately slow, just a little slow, etc. 

Tempo gives the general speed with which a musical composition moves, which gives a basis to how fast or slow we can expect musical sounds to appear. Although tempo may not be constant in a particular musical piece, once it changes from one speed to another, everything moving in music becomes proportionately faster or slower. If musical sound 1 plays for 3 seconds while musical sound 2 plays for 1 second, changing the tempo will make both of them similarly slower or faster, but the relative length of the first sound as twice long as the second sound will not change. Instead both will have durations maintaining this relation but as an absolute value, proportionately changing speed. 

For example, if the tempo is made thrice as slow, musical sound 1 will be 9 seconds long while musical sound 2 will be 3 seconds long, and although their actual durations have changed, sound 1 is still thrice as long as sound 2 even after changing tempo. In this way, tempo gives a regular flow to music in time. 

Metre and time signatures 

The beats on which a musical composition is based, of course do repeat in time as a single unit, but musical time can be followed in an even better way, by grouping these individual beats, into groups of a certain number. This is meaningful because, much of music is based on a regular repeating group of beats, and this group is called a metre. Each such group gives a bar or cycle of rhythm in music, which is the most certainly repeating amount of time. Music can be measured using these bars/cycles or groups of beats, and they give music an identifiable structure in relation to time. 

So, a bar of music can have 2, 3, 4 or even more beats. Bars with 2, 3, 5, 7 or such a number of beats (prime numbers) sound as different variations, because any of these cannot be measured equally just by multiplying the others. Bars with 4, 6, 8, 9, 10, 12, 14 or such a number of beats (composite numbers, or not prime numbers) sound longer, but can be gotten by multiplying a prime number some number of times. 

So, a 4 beat bar feels like a 2 beat bar repeated twice, and a 6 beat bar feels like a 3 beat bar repeated twice. Bars with 2, 4, 8 and other beats (powers of 2) have a distinct 'even' sound to them, while bars with 3, 6, 9, or 5, 10, 7, 14 and other beats have an 'odd' sound. In general, groups of 2 and 3 (sometimes 4) beats define 'even' and 'odd' movement of rhythm, and the others, like 5, 7, etc. can be seen as groups of 2 and 3. This is because it is not natural to count in long groups in the same way, since that has not much contrast. 

Most musical styles tend to have some repeating time that is identified by some repetition of 2's and 3's. The choice of the number of beats in a bar completely depends on the style of music, but bars of 2's and 3's are most representative and almost every region of the world uses one of these somewhere in its music. I would call these as variations of the same basic concept. 

However, not all music can be measured by repeating groups of beats. There are pieces of music using such a flow of sound that they don't fall into patterns that can be measured by such a repeating group of beats. Such music is called music in free rhythm, where the general relation of music to rhythm is arbitrary. So the basis of a repeating metre gives rhythm. 

However, the movement of music may also be between properly rhythm and free rhythm, where there is a clear beat but the musical sounds fall in an uneven, shifted way from the beat, by making some sounds longer and some shorter to fill the same time as with fixed rhythm. This is called rubato. 

The characteristic repeating measure of bars in music, is called a time signature. This can be defined in 2 ways, and of course in both, the number of beats in a bar is a defining feature. But other than, this time signatures (and even rhythm in general), can be defined in divisive or additive ways. 

A divisive definition of a time signature includes the number of beats in a bar, and the note values, or length of each beat in the bar (and in the whole piece of music) in relation to a fixed unit of length. Time signatures with the same number of beats in a bar are then the same in this system except for the length of a unit or beat, and in music, there can be any pattern dividing the beats of a bar. In this system, rhythm is measured by describing how patterns sounds and silences are divided by bars and how they are interconnected, and their patterns (rhythmic patterns) are variable. 

An additive definition of a time signature also includes the number of beats in a bar, but other than that, it gives a smaller fixed grouping or division of beats within a bar (for example, 6 can be divided as 3 + 3, or 2 + 2 + 2). Under this system, two time signatures with the same number of beats in a bar but a different division of beats will be considered different, and such a division is used as a basis for variations in patterns of sound and silence, but beyond that these patterns may move variably. Rhythm is described, in this system, by describing how groups of sounds and silences are combined to form patterns and how they are divided by bars and their divisions. 

So, divisive and additive systems are just two alternative ways of describing rhythm, and the usage of each depends fully on the musical style using them. For example, most styles of European (and other Western), Sub Saharan African and East Asian (including both Northeast and South East Asia) music, use a divisive way of describing rhythm while most styles of South Asian, Central Asian, West Asian, North African and even some Southern European music, use an additive way of describing rhythm. Any music can be described in either way, but may have been composed using only of these. 

Rhythm and rhythmic patterns

In a frame of a defined time signature, a pattern of sounds and silences in music gives a rhythmic pattern. The musical sounds can fall on the beats that evenly coincide with the first beat of a bar (for example, in a bar of 4 beats, the first and third beats are more similar than the other 2, because of the repetition of twice of 2 beats, to give 4 beats), maintaining the regular flow of beats. 

Or, they can fall on the beats not coinciding in this way with the first beat after leaving the coinciding beats empty, so that the non - coincident beats sound stressed and the regular pattern of beats is shifted because of this. This off - beat playing of sounds is called syncopation. Musical sounds can be of arbitrary length and play anywhere within a bar, and silences separate any sounds which don't come immediately after the other. Most music has some mixture of sounds and silences, and a mixture of on - beat and off - beat playing of sounds. This gives music a developing movement and a dramatic and surprising sound. 

Musical sounds and silences of various lengths can be combined in some order, into a group, which gives a basic rhythmic pattern, called a rhythmic cell or motif. It is easy to identify and describe music using these cells or motifs, and some repetition and variation of such cells or motifs is often used to give structure to music and make it sound consistent, familiar but still changing. This is similar to making words out of letters. A rhythmic cell or motif can be described using the following factors:

1. Total length of the rhythmic cell/motif and where in the bar the motif starts
2. Distribution of sounds and silences, and length of each sound and silence within the cell/motif
3. The actual sounds played

Then the cells or motifs which play together in a musical piece, can be added to give lines, or phrases of music. Phrases are like a full sentence, complete within themselves. A phrase makes music move and reach somewhere, and the next phrase then takes music to some other place. Phrases may often be somewhat regular in most music that has rhythm, giving a uniform rate at which music develops, while in free rhythm, phrases are arbitrarily long. 

These phrases are then joined in a nice order to give a musical piece. Music with a significant, well - defined use of rhythm can be structured by creating the rhythmic patterns that occur in it, and the sounds used to play these. The sounds in rhythmic music may play one after the other, or with a smaller different separation. Sounds added to the main sounds of rhythmic patterns to decorate them or enhance them are ornaments or embellishments. In rhythmic music these have to be separate from the main sounds in rhythmic patterns. 

Other than a single sound and a simultaneous playing of different sounds, which gives a different combined sound, sounds can have a very small separation, so that when played one after the other, they almost sound like a single sound, this is called an acciaccatura/flam, or small sounds leading to a main sound just played before it, called pickup notes/appoggiatura/drags/ruffs, or there could be very fast, repeated sounds or groups of sounds, called tremolos/rolls and runs. 

Structure of a rhythmic composition, rhythmic texture

Like anything moving in a limited amount of time, music has a beginning, a middle and an end. Music in rhythm can start either from the first beat of the first bar, or before it. When it does not start on the first beat, the beginning part of music which fills a partial bar is called the anacrusis or pickup. 

The beginning can start with some introduction to the musical piece and then move to some main lines which form the head of the composition, or may be made to directly begin with the main lines of the composition. The introduction or intro can also be called a prelude or overture. The main lines at the beginning part of a composition are generally the part of it which can be used to identify it, and also the most probable part of the music that will repeat as a refrain, and this could be called the theme, exposition or main verse of the piece. 

After this beginning, the music progresses into the middle, which is generally a bit different to the beginning and probably contrasts with it, to give a clear sense of movement. Since this is a consistent development of the music from the beginning, this middle is called the development, a variation or a following verse. A repetition of the main theme may follow this, and be continued by more of such movements to different developments and returning to the theme any number of times. 

Then finally when the piece comes to its ending part, the music repeats its main theme or plays some variation of the theme, returning somehow to the original structure, and having some clear ending, which can be called a recapitulation, coda or outro (the opposite of intro). This ending or cadence is usually conveyed in some clear way, such as repeating some pattern some number of times, or becoming more regular in reaching the end, or even fading slowly into silence.  

Most often, the end comes to rest in more than one way. In relation to rhythm, most music ends at the first beat of a bar, so that, after moving in whichever way, it reaches its beginning or basic reference point. The sound falling on this very last beat is in some way a basic reference sound in relation to which other sounds are perceived, usually with respect to tone or pitch relation (I will discuss form of musical sounds, the main aspect of music other than rhythm, in another post). These ways of ending by returning to a reference point are generally strongly expected by most listeners, and when not done, the music will sound incomplete to most people. 

Now the musical structure described above is true for music (and dance) that has rhythm, in general. But then, what makes a musical composition actually rhythmic? The importance of rhythmic movement and patterns in the structure of phrases and motifs/cells, clear, well - defined rhythmic patterns that can be properly heard, and the use of appropriate instruments which give a definite sense of rhythm (this is explained in the next part below) just by hearing, are all essential to rhythmic music. 

Rhythmic music must have rhythm, of course, so it cannot be free rhythm, and the use of rubato should be limited. The sounds have to play and reach our ears exactly at the required time without lagging or smoothly sliding, so sounds which can change discretely whenever required have to be used. The detection of the exact time at which these sounds play should be clear to the listener, and this depends on the sound quality and way of playing sounds, of an instrument. 

Truly rhythmic instruments can give a clear sense of rhythm without accompaniment from other instruments (this is explained in more detail below, in the next part). I prefer rhythmic music which is balanced between repetition and variation, regularity and irregularity, straightforwardness and complexity. I think that complexity is good if used to achieve beauty without losing clarity and consistency, but not necessary.

Rhythmic texture refers to the relation between the rhythm of the different layers of a musical piece, and their relation to the beats of the time signature. Most music has rhythm that obtained by multiplying a beat into equal divisions, and musical sounds occupy some of these divisions, so that the beats divide the whole of music equally, and the different layers of music also have an even relation, and this arrangement gives a homorhythmic texture. 

But sometimes, music can move such that its metre, or number of repeating units, is different from the metre of the beats of the time signature it is in, so that the beats don't divide the musical layers equally, and this could also happen between two different layers of music. For example, musical sounds that move in groups of 3 cannot be divided equally by a time signature of 2 beats per bar, since 2 does not divide 3. This gives an unequal relation between the metres of the musical layers and the time signature, and such an arrangement gives a polyrhythmic texture. 

In general, polyrhythms are played mostly by shifting homorhythmic arrangements for some time, and are more often a deviation from homorhythms to give variation, although sometimes a whole musical piece can be polyrhythmic. But even then, homorhythmic arrangements are what all musical styles generally use a lot generally. In most music, there are at most 2 layers with independently changing rhythm (more often only one fully independent layer), since more than this makes music sound unclear and a bit chaotic, and even with 2 independent layers there is some coordination between the rhythms of both. 

There may be a number of more layers that are mostly repeating the same rhythms (called rhythmically ostinato), and give accompaniment and support to the main independent layers.

In the next part of this post, practical aspects and intricacies of performing and indicating rhythm in music are explained. Please read it here.

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