[Please note that some of the figures and tables referenced in this chapter abstract are not included presently, but we hope to update the article with the necessary graphics eventually as they become available.  Thanks for your patience.  JANPress Publications ]

Why include a chapter on Sound in this book?  Every recent book on computer music has a chapter on sound.  At the risk of being redundant a chapter on sound is necessary for several reasons.  First, we need to understand the basic mechanics of sounds.  Then, we can understand the complexity of sounds and music.  Finally, there are many interrelated variables associated with music.  These variables are many and complex.  Computers are a tool to help manipulate these many musical variables.  Some of the information in this chapter may be familiar to you.  If so, be patient as we discuss how computers have made the manipulation of the complex and myriad sound variables relatively easy. 

Let's examine what the musical variables are first in natural music.  Later, in the discussion on electronically created music, we will see how these variables are recreated and manipulated electronically.  Finally, we will see how new sounds, or even musical instruments, if you will, are created. 

The first element in the discussion of music is the nature of sound.  How do we create sound?  What causes sound?  How do we distinguish noise from music? 

The basic element of sound is the movement of air.  Vibrations of air, also called OSCILLATIONS, cause acoustic (or natural) sound.  These vibrations result in air movement.  These air movments can be thought of as or mentally pictured as air (or sound) waves.  It is a cliche that sound waves are comparable to waves in a pond.  If you throw a rock into a pond, you will create a big splash, followed by concentric ripples that gradually diminish in size.  A certain portion of the trough created by the wave or ripple will be above the usual level of the pond.  Another portion of the wave or ripple will be below the level of the pond.  The level of the pond can be thought of as the BASE LINE.  The peak of the wave is above the base line.  The trough of the wave is below the base line.  Sound waves travel through the air in much the same way, creating sound in the directions of the wave's travel until it diminishes to inaudibility.  See Fig. 3-**.

In natural acoustic music there are many ways to cause air to vibrate as sound waves with musical instruments or the voice.  Air is set in motion by bowing, plucking (or strumming) or striking an object of some kind, thus creating vibrating sound waves.  Another way of causing air vibrations is by blowing wind through a pipe of some kind.

You can divide musical instruments into three basic classes.  These three instrument classes are string, wind and percussion instruments.  More details of each class of information follow with their classification, according to the Encyclopedia Britannica. 

Stringed instruments are CHORDOPHONES.  The suffix chord in the word chordophone refers to strings.  You create sound on stringed instruments by bowing, plucking strumming and, sometimes, striking the strings.  Examples of stringed instruments bowed or plucked are the violin family of violin, viola, cello and double basse.  Stringed instruments plucked are the harp or guitar, preceded historically by the lyre or lute.  Finally, an instrument that we sub-classify in the keyboard family of instruments is the piano.  The piano was preceded historically by the clavier and the clavichord.  A piano is correctly classified as a stringed instrument because it consists of several strings struck by a key. 

Wind instruments fall under the classification of AEROPHONES.  These are further subdivided into groups of brasses, woodwinds, free reeds and pipes. 

The brass group of instruments includes the trumpet, baritone, trombone and tuba.  You create sounds in a brass instrument by blowing air into a tube.  The conical shape of the tube forces the air to constrict.  This constriction in turn causes the air to vibrate faster.  Air speeds up when forced into a constricted aperture, such as a horn.  This is similar to the principle used in jet propulsion. 

Another class of wind instrument is the woodwind family.  You can break this class down further into reeds such as the clarinet family or  double reeds, such as the oboe, English horn or bassoon.  The accordion and harmonica types of instruments are wind instruments.  These instruments are not usually tought of as wind and reed instruments.  However, upon closer examination it makes sense when you realize that reeds in the instruments vibrate under wind pressure, creating music.  These types of instuments fall under the sub-class of "free reeds."

An instrument usually classified as another keyboard instrument is the pipe organ.  It is a wind instrument because air is forced through pipes of various sizes and lengths to produce different tones. 

You could say that the voice is a wind instrument because you force air under pressure through the voice box.  This causes the larynx  or voice box to vibrate, creating air compression and sound waves.  Because the sound waves created by the human voice are much more complex than those of musical instruments recreating the human voice singing is geometrically more complex even with the use of today's high technology and computers.

The percussion instruments are IDIOPHONES or MAMBRANEOPHONES.  The bodies of idiophones vibrate when struck to produce sounds.  Idiophones instruments include pitched instruments such as the glockenspiel, xylophone and marimba.  Non-pitched percussion instruments include the snare drum as the most common example. 

Membraneophones produce sounds by striking membranes.  Membrane instruments originally had animal membranes stretched over the drum head but now are plastic.

The fourth way air is vibrated is through electronic music.  We will discuss electronic music in detail later.  In this chapter and later in Chapter Five we will see how electronic instruments such as the synthesizer has added a completely new dimension to the process of creating sound.  Let us continue for now, though, with the discussion of music based on acoustic or naturally created sound.  Keep in mind that later we will discuss how the same musical natural music elements can be recreated closely with electronic music.

Music consists of melody, rhythm and harmony.  These elements will be examined in detial later.  We can also break down music into even smaller units called notes.  Notes consist of pitch, duration, volume and timbre (tone quality.)  Let's discuss the properties of notes first.

You can subdivide the pitch of a note into even smaller elements.  Pitch refers to the name of the note as well as its height.  How high or low a note sounds to the ear depends on the number of times per second the air is vibrating.  FREQUENCY is the number of vibrations per second.

In music air vibrates at a regular rate called a CYCLE expressed in Hertz.  A cycle is the portion from beginning to end of the vibrations in each beat or pulse in the note.  Again, picture the ripples in a pond.  A cycle could be thought of as the point from the peak of one ripple to the peak of the next.  The range in which the human ear can distinguish sound is usually from 20 Hz to 20,000 Hz.  That is, from 20 vibrations of air per second to 20,000 vibrations of air per second.

The note used in tuning an orchestra is an A 440.  A 440 is the note created by air vibrating at 440 cycles per second.  Another term for this is frequency.  The frequency of this note is 440.  Another word used to describe a note played is PITCH.  Pitch refers to the note name. 

In Western we group musical pitches into what we call OCTAVES.  Octaves start at one frequency and end when the frequency is either doubled or halved.  For example, the octave below A 440 is A 220.  The octave above A 440 is A 880, etc.  In Western music octaves are divided into twelve basic pitches. 

Before discussing these pitches let's examine ACCIDENTALS.  These are symbols used to raise or lower a pitch.  The symbol used to raise a pitch is a # which stands for SHARP.  The symbol used to lower a pitch is a b which stands for FLAT.  Sharps and flats are ACCIDENTALS.  Another accidental called a natural cancels a sharp or flat. 

The twelve pitches in an octave in ascending order are A A# B C C# D D# E F F# G and G#.  The twelve pitches in descending order are A Ab G Gb F E Eb D Db C B and Bb.  Note the absence of accidentals between notes B and C and between notes E and F.  If you look at a piano you will see clearly that there are no black keys between B and C or E and F.

If you start on the note C and play eight successive notes higher skipping the accidentals you have played a C Major scale.  Doing the same procedure starting with the note A results in an A minor scale of which there are three main versions, the natural, harmonic and enharmonic scales.  Refer to a book on music theory if you would like to study the details of these scales.

Looking at a piano you will note black and white keys.  The distance or interval from one key to the next key closest above or below the starting pitch is a half step.  You can TRANSPOSE scales by starting on any note of the 12 pitches and playing the same intervals found in the C Major scale.  That is from the C to D is a whole step, from D to E is a whole step, from E to F is a half step, from F to G is a whole step, from G to A is a whole step, from A to B is a whole step and from B to C is a half step.  Thus, you can create a major scale starting with any ptich and playing intervals of a whole step, whole step, half step, whole step, whole step, whole step, half step.

If you play a scale starting on the notes D, E, F, G, or B you play scales usually called MODE scales.  Based on the notes named in the previous sentence, these modes are the Dorian, Phrygian, Mixolydian and (** look up the names of the other modes**)  This applies to Western music.  Eastern music uses a five note scale or pentatonic scale.

Since pitches only have twelve note names, it is often convenient to refer to a pitch's octave position.  If you measure the octaves in a piano with the first octave being octave 0 then A 440 is A4 440.  To be precise it is A4 442 Hz.  For example, a C ** is middle C.  An A 440 is an A **nn.  The words pitch and frequency are often interchangeable.  To be technically correct, pitch refers to the name of the note.  Frequency refers to the number of vibrations per second of the sound waves.

There will be more details on music theory later in Chapter Seven when we discuss music theory software.  Let's discuss musical intervals briefly now.  We talked about intervals of an octave briefly in the above paragraphs.  An octave is an example of an interval. 

 Starting with any root note, for example C, and proceeding upward or downward, we can measure the distance between notes in intervals.  Understanding intervals becomes very important later on when we discuss harmony, triads and chords.

Following is a list of the distance or intervals from C up one octave to C:  (**insert table here.)

Following is a list of the distance or intervals from C down one octave to C:  (**insert table here.)

You will hear musicians tuning the pitches of their instruments before a concert.  Pitch is affected by temperature, humidity, room size, etc.  An orchestra must achieve uniform pitch to sound in tune.

You can change the pitch of a note  to higher or lower by increasing or decreasing the rate at which air is vibrated.  This can be done in several ways, depending on the instrument. 

One way to change pitch in a stringed instrument is to change the size of a string.  To lower the pitch you increase the size of the string and vice versa.

Another way to increase a note (or raise the note) in pitch in a stringed instrument is to shorten the length of the string.  Conversely, you can decrease the pitch by lengthening the string. 

One obvious way this is done is to use longer strings with larger instruments to lower the pitch of the string and vice versa.  The double bass, the largest of the stringed instruments, is an octave lower in pitch than its written sheet music indicates.

The usual way of shortening or lengthening a string to change the pitch in a stringed instrument is by touching the string with firm finger pressure.  This pressure applied to the string along the fingerboard at measured intervals causes the notes to change by any tone along the scale. 

A variation of this system is to touch the string lightly with finger pressure at points that partition the string into halves, fourths, eighths, etc. This creates soft notes called HARMONICS.  There will be more about harmonics later in this chapter.

You change the pitch in a wind instrument similar to a stringed instrument.  One way to increase the pitch of a note in a wind instrument is to shorten the length of the tube.  This is done by using three fingers (sometimes four on some french horns or tubas) to press open valves.  These valves open airways to tubes that result in increasing the length of the tube.  Conversely, lifting the fingers off the valves decreases the length of the tube.  As in stringed instrument, you can lower the pitch by using a larger instrument and vice versa.

Another example of the way you increase the pitch in a wind instrument is by increasing the number of vibrations of the air.  You tighten the lips more as you start a note by buzzing your lips, as when blowing into a brass horn. 

You increase or diminish the pitch in a percussion instrument in similar ways to the above.  To increase the pitch you can increase tension on the surface of the percussion instrument and vice versa.  You can also increase the size of the instrument to lower the pitch, as in a bass drum.  Pitched percussion instruments work in similar ways.

Since early history mankind has worked to find ways to preserve musical variables.  One of the reasons for this was to pass music from one region to the next or one generation to the next by paper rather than rote memory.  Eventually, music notation preserved musical pieces and promote the ability to hear musical pieces over a widespread geographical area. 

The transcription of musical variables onto sheet music became sophisticated and fairly accurate.  This was no mean feat considering the enormous amount of musical variable data that had to be converted into universally understood symbols.  Computers now hold the promise of making music transcription into sheet music potentially easier than ever before.  Another possibility is that computers will make the transcription of sheet music uneccesary as computer symbols replace the need for sheet music symbols.  However, the time for sheet music obsolescene still appears far away.  Meanwhile, it is helpful for most of us to learn and use standard music notation.

In musical notation you express pitch in the following way.  The first step is in writing music is to create five horizontal lines called a STAFF.  More than one staff is called STAVES.  The relative position of the note on the five lines determines their pitch.  The pitch varies according to the identifying CLEF at the beginning of each line of staves.

Sometimes called the movable clef, the clef names a certain note on the staff as the identifying pitch.  The treble clef is also called the G clef because its main circle encompasses the note G on the second line from the bottom of the staff.  This clef is perhaps the most familiar.  The bass clef has two dots which encircle the fourth line from the bottom to identify the note F.  Other clefs commonly found are the tenor and alto clefs. See Fig. 3-**.

A tapping at a regular interval produces a BEAT.  A beat is one way of dividing time in music so notes can have a measurable duration.  At certain regular points in music you insert bar lines to identify when specific amounts of time or groups of beats have passed.

     You can subdivide notes downward.  The division in descending order are:
     whole notes which usually have four beats 
     half notes which have two beats
     quarter notes which have one beat
     eighth notes which have half a beat