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• Introduction

Introduction:

-MTO /0 /land botlk

. ButYou Should Read This One

This booklet is designed to make your classroom experience in Berklee's MTO I 0 Introduction to Music Technology course more productive and more pleasant. It lightens your note-taking load, and makes it possible for teacher and students to do what humans do best-interact.

Nothing takes the place of learning by doing, and opportunities using Berklee's unparalleled facilities are provided in this course to do just that. Learning also occurs in the time-honored way of the musician-by being shown. The demonstrations in class will be much more vivid if you can focus on them without furiously scribbling "notes" that you have to de­code later!

Obviously, this written material is not a substitute for classroom participa­tion. Nor will it "teach" you things that you must do or be shown in order to learn. But it will provide a framework of tenus and concepts that sup­port your understanding of the music technology that is around you. The typography of this text also supports your review of the material for exams, with words in bold that summarize important ideas.

This booklet answers some of the "what" questions about music technol­ogy. Your classroom experience and hands-on opportunities will answer some of the questions about "how." And if you persist, you may come to see that "music technology" has always been with us-it is not some foreign idea unique to your time and this place. You will then begin to provide yourself with the tools that help you give personal answers to the many "whys?" that have motivated the creative musical act through the ages.

And, as always, if you discover something that gives meaning, increases freedom, or brings joy-share it with your friends!

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Sound Pro . es ;;;;;;;;;;;;;;;=

There ' s an old riddle about sound that asks: if a tree falls in the forest, does it make a sound if nobody is there to hear it? The heated debate that can arise depends on how you define sound. One dictionary tells us that sound is "mechanical radiant energy that is transmitted by longitudinal pressure waves in a material medium," while another definition defines sound as "vibrations in air, water, etc. that stimulate the auditory nerves and produce the sensation of hearing." You can find a definition to fit either answer to the riddle, depending on whether trees fall in splendid isolation or in your back yard while you're cooking barbecue. Is sound energy that is transmitted even if nobody is listening, or is it the sensation of hearing, which requires a listener?

Scientific instruments can sense, record, and report on vibrations of the earth (seismic), or the air (sonic). No listener need be present for these devices to prove that sound as energy that is transmitted occurs when a tree falls. If several instruments report this "sound" you would expect agreement among them, for well-designed scientific instruments provide us with objective information. That is, information that is directly measur­able, real or actual, independent of the mind's interpretation. And you aren't surprised to fmd that this kind of information is expressed using numbers expressed on a scale people have agreed upon.

On the other hand you expect listeners to talk about sound using language that is subjective, affected by, or produced by the mind or state of mind. Subjective information typically is not subject to being checked externally

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or being verified by other persons. About the best you can do is to survey a group of people to see if there is any agreement about what they hear.

For centuries musicians have described sound subjectively, using words like sharp, flat, loud, shrill. bright, dark. incisive. loud. soft. etc. Musicians have recognized the general properties of musical sound: pitch, timbre (tone color), loudness, and duration. If we think of duration as simply the timing of loudness. it is simpler to say that musical sound has the subjec­tive sound properties: pitch. timbre, and loudness. These properties are quite real to us, and there is much agreement concerning how we hear them. but they are subjective nevertheless. Subjective properties of sound have to do with the sensation of hearing. Musicians recognize the interval of an octave and respond in predictable ways to dynamic markings such as ppp. mf, and ffJ. but these sound properties rely on (subjective) human judgment and musical experience .

------------------------------------------------------------------MTOJO Handbook

Chapter J • Sound Properries

Musicians have traditionally given little thought LO the individu::ll pro er­ties of sound-objective or subjective, because acoustic instruments gener­ally don ' t offer independent control over sound properties. T:.e ph. _icai characteristics of acoustic instruments dictate that control or-sound pro ~r­tics is somewhat integrated For example, because of its construction. the clarinet has a characteristic timbre (tone color) for each of Its ihree pi<ch registers. It would be difficult to play high notes with me timbre rloun:!lly associated with the low register. The trumpet has a built-in relation,hi t

between timbre and loudness: soft sounds tend to be mellow and lou':: sounds are brilliant. For thousands of years musical instrumems naye hJ." this characteristic integration of control of the properties of sou,'lu. You just can't tear instruments made of metal and wood apan easily t:) at ow independent control over sound properties. Historically. mu-ic:311: h:I"e had little interest in the science of sound because so little eouid ·-.e about il

Electronic technology is changing our possibilities for olltrOllL'l,:, ur:. and the concepts we have in making music. ~ow, with electronic me2-': we cart override some of the built-in tendencies of aco ti in.:mun nt.:-­we hope for artistic effect. For instance, screaming-loud uumpe C:1.

recorded and reduced to a low level in the final mix: In thi~ a.se. in ~eDen­dent control of loudness and timbre can create a brilliant. ut "uie IT'~-::p . sound-overcoming the "natural" characteristics of the inst:rurni!.lt. ~LY -this is what early composers tried to achieve when they \\ ..... ••

trumpet parts?!

In fact, modern electronic musical instruments and rec rdin"" ue . _ :e-", , maximize the segregation of sound properties. Some ynth.> ·ze :~t \ . -deal with sound properties individually at a mi ros opi ley 1. Tn.> i.: _ growing tendency to express sound properties numerical.ly. aI1u in ~h~

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language of the objective sound properties: frequency. sp trum." Bye--shape, and intensity.

Objective language has a clear meaning regardle-,,,, language, culture, gender, etc. The perfollner~. re" designers and others who understand thi langu ge i: -

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wish to shape and control sound. On the oth r h nd. th' ear-a SUbjective organ to be sure-has the 1 t \\t rd n In ':i' Music is for people-nol machines ! The m r', u . I.. \\ :1 t -and subjective sound propenies. the Ie u: th!: . r diction will seem.

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Chapter 1 • Sound Properties

Pitch-

MTOJO Handbook

You tune up before playing by matching the pitch of your instrument to

some tuning reference such as "A above middle c." It so happens that the pitch of the musical note known as "A above middle C" has varied widely over the centuries in different countries. Only in this century has "A-44 0" been accepted to standardize the tuning of modern instruments and the pitch of our musical scale. But what does "A-440" mean? The number "440" represents a frequency standard, meaning that a sound that repeats its vibration 440 times per second will occupy the "A above middle C" position on our musical scale. Note the use of numbers and the standard­ized time unit second to describe this objective property of sound. We judge the pitch-we measure its frequency.

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Let's see how pitch and frequency relate. We hear pitch as the highness or lowness of a sound. The piccolo plays high pitches; the tuba plays low pitches. Our perception of pitch is complex, but depends mostly on how frequently and regularly sound pressure waves strike our ears. Many children make a "motor" for their bicycle by attaching a piece of card­board so the spokes strike it regularly. TIle faster the wheel turns, the higher the pitch of the sound caused by the spokes striking the cardboard. That's because the individual spoke sounds are heard more frequently­there are more repetitions per second. Pitched sound is a periodic phe­nomenon in which a particular vibration pattern repeats regularly. Fre­quency is defined as the number of times a given pattern repeats in a unit of time-usually a second. Frequency is expressed numericaUy in Hertz (abbreviated Hz), or in outmoded tellIlS cycles per second (abbreviated cps). The modern pitch standard produces an "A above middle C" with a

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Chaptu J . SOllnd Properties

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frequency of 440 Hz. Although the correspondence between frequency and what we perceive as pitch is not perfect, a higher frequency is generally heard as a higher pitch.

For the scientist who measures frequency in Hertz, an octave is defined as a 2: J ratio. That is, the octave above the note A at 440Hz is twice that number, or 880 Hz. The octave above the note A at 7,040 Hz is therefore 14,080 Hz. But the musician judges an octave or any other musical inter­val by ear. And research has shown that the pitches musicians judge to bc the interval of an octave do not always have a 2: I ratio in frequency. We tend to judge the extreme highs and lows of the perceptible pitch span differently than the middle portion. We tend to want to stretch the high frequencies higher, and the low frequencies lower to satisfy our musical sense of pitch. Because of human anatomy your ear/brain perceives pitch on a nonlinear, or curved response to the frequencies heard. Your ear doesn't operate on the predictable linear, or straight line of a 2: 1 frequency ratio for the scientist's octave. And to make things worse, not all musi­cians perceive pitch on the same curve!

Timhre-Waveshape/Spectrnm

If everyone in the group plays the same note A-440 when tuning, what is it that lets us tell one instrument from another? Why does each instrument have a distinctive tone color even when playing the "same note?" It's easy to tell one class of musical sound from another by how each sound starts and ends. Whether a sound is bowed, blown, struck, etc. helps you judge what kind of instrument is involved. This transient behavior involves the attack and release, or how a sound begins and ends. and affects how we tell which instrument is playing.

Also, if you view a steady tone made by a musical instrument on a scien­tific instrument called an oscilloscope you see a distinctive waveshape. This waveshape appears as a single line on the oscilloscope, a device that can dynamically graph sound pressure level (SPL) as it changes in timc. Since waveshape is a representation of sound in time, this depiction is known as the time domain. Time is depictcd along the horizontal aus. and the amplitude. or size of the waveshape is shown on the vertical axis. If the wavcshape is audible you perccive its amplitude as loudness. In the time domain it is easy to idcntify classic waveshapcs such as the sawtooth, square, triangular, becausc each shape suggests its name.

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Waveforms· Time Domaitl Representation

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With a few exceptions, different waveshapes are heard as different tim­bres. Most acoustic instruments have a distinctive waveshape that helps us identify that instrument's unique timbre, or tone color. If an elec trical signal generated by a sampler or synthesizer has the same waveshape as a sound created by a traditional instrument (other factors such as transient behavior considered) their sounds will be similar. Of course, just because you can produce waveshapes of acoustic instruments doesn't mean you can perform like people who have devoted a lifetime to the study of those instruments !

Looking at a waveshape is not necessarily the best way to know what sound it will make. There is another way of representing sound graphi­cally, the frequency domain. The differences you hear among various static, or steady-state musical waveshapes are due to differences in their spectra (plural). The spectrum (singular) of a particular waveshape comprises a collection of simple components, each of which is called a pal tial. Each partial is a sine wave having a unique frequency (hence frequency domain) within that particular spectrum. A sine wave is a representation of simple hallllOruc motion (abbreviated SHM) which can be derived from circular motion, and illustrated by the pendulum of a clock. A sine wave is a "pure" sound that cannot be simplified (it isn't a collection of partials-it is a partial). The closest sounds we have to illus­trate a sine wave are a tuning fork tone (especially when aided by a reso­nating box), singing "00" softly in falsetto, or the tone produced by blow­ing across the opening of a bottle. A spectrum, or frequency domain representation of a sound looks like a bar graph, or histogram . Each partial is represented individually as a single vertical line on the hori­zontal axis indicating its frequency. The height of an individual line represents the strength of that partial: the amplitude of a partial is repre­sented on the vertical axis .

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Chapter J - Sound Properties ---------

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Harmonics and Nonharmonics

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A periodic, or pitched sound in the world of music is usually not a simple sine wave, it is a complex waveshape. The sound of a complex waveshape is the result of the simultaneous vibrations of its several partials. Many complex waveshapes consist of a first partial called the fundamental. and other partials of higher frequency and smaller amplitude. When thc frequencies of these upper partials are whole number multiples of the frequency of the fundamental, the partials are called harmonics. For instance, a complex waveshape with a fundamental frequency of 100 Hz might be composed of simple sounds (sine waves, or partials) having the frequencies 100 Hz, 200 Hz, 300 Hz, 400 Hz. and so forth. These frequen­cies are whole number multiples of the fundamental frequency 100Hz. and are therefore harmonic. Whole numbers are integers. and all the partials of a periodic, or pitched sound are harmonic. meaning the partials have an integral relationship to the fundamental. Upper partials that are harmonic tend to reinforce our perception of the fundamental frequency as the pitch we identify. The presence and relative strengths of halIllonies-thc harmonic spectrum-accounts in part for our perception of the timbre, or distinctive tone color of many musical instruments.

What if a partial is nonintegral: not a whole number mlllTiple of the fundamental? For instance. in the collection of partials: 100 Hz. 215 H7. 300 Hz, 400 Hz. 550 Hz the partials tuned to 215 Hz and 550 Hz arc 1Io r

whole number multiples of the fundamental. Each of these partial is a nonharmonic (sometimes called inhallllonic). A bell sound. a so-called clangorous sound, usually has several nonharmonics in iL~ spectrum . Sometimes there is no' clear fundamental frequency in a clangorous sound. and partials typically exhibit nonintegral relationships. If there is a mn­dom distribution of partials over the entire auditory rang.:, we hear noise . whIch sounds like the static between stations on FM radio

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. Chapur 1 - SoU!lt1 Prop~n~

Loudness-Intensity/ Anlplitude

MTOJO Handbook

If you look at a guitar string as it vibrates, it is apparent that the distance that the string moves is related to how loud the sound is. The amplitude, or size of the vibrations, and the objective sound property of intensjty are obviously related to the subjective sound property loudness. But it is difficult to measure intensity directly outside the laboratory, so we mea­sure sound intensity indirecLly using devices like a sound pressure (SPL) meter using the decibel (dB) scale. If we view a static audio waveshape on the oscilloscope we can measure the signal amplitude (usually expressed in the electrical unit of volts) on the vertical axis, and this also relates (0

the loudness that we hear. Using either device, we are nOt measuring intensity directly, but an electrical signal that represents intensity. \Ve often say that an electrical signal has a certain level , another name thal indicates size.

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Of all the sound properties, loudness is the least well-behaved wheo we try

to make it fit an objective property like intensity or amplitude. Imagine that you listen to a quiet but audible sine wave whose amplitude remains unchanged. You adjust its frequency over the tOtal span of human hearing. What happens to its loudness as you change the frequency? You won't hear the sine wave equally well a1 every frequency. Loudness. which we perceive subjectively, varies even though the objective signal amplitude does not. In fact it would sound quite loud at 3.000 Hz (3 kiloHertz. or 3 kHz) and might not be audible at all at 30 Hz or at 15.000 Hz. If you graphed your ear's response you would see another curve, indicating a nonlinear response to a sine wave whose amplitude remains the same as its frequency is changed. On the other hand a very loud sine wave with a fixed amplitude sounds at about the same loudness at low. mid. and high frequencies.

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Iffact, there are several sets of equal loudness curves for sine waves that illustrate this experiment, the earliest due to Fletcher and Munson. These curves graphically show that the ear is more linear, or "flat" in its response at very high levels, and extremely nonlinear at lower levels. But you've probably had a vivid example of the ear's nonlinearity regarding intensity/ loudness if you simply recall it: when the phone rings and you tum down your stereo, what changes about the music? The lowest bass and highest treble seem to disappear when you play music at a low level. This isn't a deficiency of your stereo-it's caused by the nonlinear response of your ears. Most stereo amplifiers have a so-called "contour" or "emphasis" switch that electronically boosts lows and highs; it's use will "flatten out"' the ear's response when playing at low levels and make the tonal balance sound better. (Don't use it when playing at high levels-the ear doesn't need it, and your neighbors probably don't either.) Try playing the same passage on your stereo at different levels to demonstrate the ear's fre­quency/loudness response to yourself!

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M.OIO

Chapter 1 . Sound Propmlu

As we see. thl century' s music technology has some specialized teuIlS and language. and we can better deal with this technology if we are famil­iar with the e tCIIIlS. In fact, there are many specialized tellBS within the field of mU,ic. For instance. words like "nut" and "frog" and "bridge" conjure up specific images for a nonmusician, but have a very different

meaning to a violinist! -

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