A glossary of terms taken from:
The Studio Musician's Jargonbuster (ISBN 0 9517214 2 9) - scrupulously
written by me, carefully published & distributed by Musonix.co.uk,
and easily available from any music shop which doesn't suck, or
Musonix.co.uk itself.
- Ambience
- The reverberant quality of a room.
- Amplitude
- The relative value of a signal, its volume or magnitude.
The height of its waveform.
- Anechoic
- Without echo. Said of an acoustic which is free field (i.
e. without boundary or reflecting surfaces), and specifically
of a room which is designed to produce no reverb or other echo
effects. This is achieved by making the walls with very irregular
surfaces of considerable and varying depths, in such a manner
as to ensure that (in theory) all sound pressure waves which
strike the walls are completely absorbed. Rooms of this type
are used to test audio equipment such as loudspeakers and microphones
and for other types of research.
- Attack Time
- (1) The time taken for a musical or other sound to reach
maximum loudness or timbre from silence. The start of a sound.
(2) Of a compressor or limiter etc. The time the device takes
to respond to a transition in the signal level beyond the threshold.
(3) Of an envelope generator
the time taken for the envelope to reach its maximum level from
its off or zero position. If the EG is being used to control
an amplifier (VCA or DCA) the time taken to reach maximum loudness
from silence.
- Attenuation
- A reduction in the the amount of some quality such as signal
level. The property exhibited by attenuators. The opposite of
amplification.
- Audio Frequency
- The range of frequencies which can
be experienced by an average human being. The range is defined
as 20 Hz to 20 kHz for convenience but in
practice, is realistically closer to 20 Hz to 17 kHz. Dolphins
are believed to hear up to 70 kHz.
- Bandwidth
- (1) The upper and lower limits of a range of frequencies
a signal possesses, or that a piece of equipment will pass. It
should not be confused with frequency response, which concerns
itself not only with the upper and lower limits but also how
frequencies are amplified or attenuated between these two points.
(2) One parameter on a parametric equaliser.
- Concert Pitch
- Established by the International Organisation for Standardisation
in 1955, the agreed reference frequency
of 440 Hz. for the note called middle A.
Notated A=440.
- Consonance Dissonance
- An aesthetic judgment of the relative attractiveness of combinations
of notes sounded together. Consonance relates to a more pleasant
experience for the listener while dissonance relates to a less
pleasant experience. The judgment of whether any given interval
falls into one category or the other has been arbitrarily applied
throughout history, with a general tendency for the progressing
acceptance of smaller intervals. The terms are also used in a
stricter sense in theories of tonal harmony.
- dB SPL
- A decibel based unit intend to give
an absolute measurement of sound pressure, where 0 dB ="20µPa
(micro Pascals). The human range of hearing is related to this
scale with 0 dB(SPL) being the threshold of hearing, while 120-140
dB(SPL) (depending on which reference book you use) being the
threshold of pain.
- Decibel
- A ratio based measure of the comparative amount of some quality,
usually sound level, power or voltage, relative to some reference
amount. It is often qualified to indicate what property is being
compared i. e. dB(A), dB(v) etc. e. g. One might talk about a
signal to noise ratio of 80 dB(v). This would be a comparison
between the amplitude of the signal
(which we want to hear) and the noise (which we don't). In this
case the signal voltage becomes the reference point, (whatever
the actual value was) and would be called 0 dB(v), the noise
voltage (whatever the actual value was) would therefore be 80
dB(v) smaller. The logarithmic nature of the decibel allows us
to compare two values of enormously different magnitudes with
conveniently small numbers. e. g. the limits of hearing in terms
of absolute pressure level cover the range from 20µPa to
200,000,000 µPa. Any arithmetic on this basis is quite
tedious. The same range expressed in dB SPL is 0 -140 dB SPL.
Much more convenient.
- Dynamic Range
- The difference in signal level between the loudest and quietest
parts of a programme, expressed in decibels.
- Envelope
- The characteristic change in amplitude
throughout time which all sounds possess. The envelope of a sound
has a number of features: whether it sustains like a bowed violin
string; whether it decays like a plucked violin string or a single
strike of a drum; and how quickly the sound reaches its fullest
intensity - how the sound "attacks". While the envelope
of any specific sound has specific characteristics determined
by the way the sound was generated, it should be realised that
real sounds occur in real situations and the envelope of a sound
will change according to the environment it occupies. A clave
in a cave may appear (what is the sonic equivalent of the eye-based
"appear"?) to have a longer envelope than when it is
played in the open air.
- Envelope Generator
- A device which produces a control signal which varies in
level with time. The simplest of these (sometimes called ADSR)
has four parameters: Attack Time, Decay Time, Sustain Level & Release
Time. Thus it has three time constants and one level constant.
Such a device is often found on synthesisers,
where it is usually used to control the volume of an amplifier,
the cut off frequency of a filter, or the frequency of an oscillator.
More complex arrangements involving a series of time and level
constants are available, particularly on digital synthesisers.
These are called multistage envelopes and may involve eight or
more parameters usually in time and level pairs.
- Equal Temperament
- A system for dividing an octave into 12 pitch steps, each
of 100 cents. This has the effect of making all semitones equal
in size. This became necessary once keyboard and fretted instruments
became popular. It should be understood that the note A which
appears in F# minor should have a slightly different frequency
from the note A which appears in C major (this fine distinction
is one of the reasons that pitch and frequency are not quite
synonymous). This would normally be dealt with automatically
by a proficient player on an instrument with continuous pitching
such as a violin. A keyboard instrument would properly have to
be tuned to a particular key, if music was then played in a different
key, some or many of the intervals sounded would be flat or sharp.
However since it was not convenient to retune these types of
instruments correctly whenever a new key was required, various
compromises were attempted. Equal temperament was one such compromise
whereby the error was distributed equally between all the notes.
This made the performance of music in different keys possible
on the same instrument without retuning, in celebration of which
J. S. Bach wrote not one, but two books, each of 24 preludes
and fugues (a prelude and fugue in both the major and minor forms
of 12 keys).
- Frequency
- In audio, the number of repeating cycles of change in air
pressure or oscillations in voltage, that occur in one unit of
time usually a second. Complex sounds are made up of many pure
tones of different frequencies. Measured in units originally
called cycles per second (CPS), now called Hertz
(Hz). For convenience, the human frequency range is divided into
three rough areas or bands. High frequencies (between about 5
kHz and 20 kHz), mid frequencies (between about 200 Hz and 5
kHz) and low frequencies (between about 20 Hz and 200 Hz).
- Frequency Response
- A graph which shows how a system or piece of equipment or
even an environment such as a room responds to different frequencies. Ideally, for audio work the
graph should plot a flat line from below 20 Hz to above 20 kHz.
In practise this is often not achieved, and the line will fluctuate
up and down between these points, indicating that the equipment
or environment makes some frequencies louder or quieter than
others. Humans have a well documented "non-flat" response
and this is the response used to specify the dB(A) scale for
determining loudness. The term should not be confused with bandwidth
which concerns itself only with the attenuation above an upper
limit frequency and below a lower limit frequency and does not
concern itself with the range between them.
- Fundamental
- The lowest frequency partial which
is present in a (normally) musical sound. See also Harmonic,
Inharmonic.
- Harmonic
- (1) A special case of partial normally
occurring in "musical" sounds, in which the frequency
of the partial has a simple mathematical relationship to other
partials. Generally they are all integer multiples of a particular
fundamental frequency. See also Inharmonic. (2) of or pertaining to musical
harmony (the juxtaposition of one note with another or others).
- Hertz
- The SI unit of frequency, in particular
the number of times something occurs in one second, abbreviated
Hz. Named after Heinrich Rudolph Hertz (1857-94). The unit is
sometimes alternatively expressed as CPS.
- Hz
- See Hertz.
- Inharmonic
- A partial or sinewave
component of a sound which bears no simple arithmetic relationship
to any other partial in the sound. See also Harmonic.
- Microtonality
- The exploitation of intervals which lie between the semitone
steps of the equal tempered scale.
This allows the use of tunings and modes which are more typical
of non-western music. This important and underestimated facility
is at last becoming available on synthesisers.
- MIDI
- An agreed standard for communication between electronic musical
equipment such as synthesisers, samplers
and other devices such as computers. The core function of the
standard is to allow information describing musical peformance
(which notes were played, how loud they should be, plus articulations
such as "bending" of notes or vibrato etc.) to be capable
of transmission from one machine to another. The recording of
such information for later replay is called sequencing. The standard
also includes many functions which are ancillary to this core
activity, for example the standardisation of files for sequences
(Standard Midi File) and digital audio recordings (Sample Dump
Standard) and methods of exchanging information that is unique
to individual devices (System Exclusive).
- Mode
- A simple definition of this complex and diverse term would
almost certainly be inaccurate, while a full discussion is beyond
the scope of this glossary, but here goes. Essentially a type
of scale. If the notes used in a melody all appear in a given
modal scale, and if the melody begins or ends on the base note
(final) of the modal scale, the melody is said to be in that
mode. The modes most commonly referred to can be obtained by
playing only (and all of) the white piano notes between certain
keys and their octaves thus: Ionian C - C, Dorian D - D, Phrygian
E - E, Lydian F - F, Mixolydian G - G, Aeolian A - A. Modes are
most commonly encountered in folk and ethnic music. The modern
major and minor scales correspond to the ionian and aeolian modes
respectively. So it seems that tonal music (most of the music
written in the last 300 - 400 years) is based on only two of
a number of possible scales, and it is interesting to note that
while much European art music has confined itself to a thorough
exploration of only these two modes, the rest of the world and
European folk musicians have been quietly exploring all the rest
and others. In defence of the apparent narrow mindedness of European
art musicians, it must be said that the other modes do not easily
lend themselves to the systematic and hierarchical structures
beloved of them.
- Modular Synthesiser
- A synthesiser where the individual
sound generators or processors such as oscillators, filters,
amplifiers, envelope generators etc. are physically separate
units which can, or have to be, connected together by the user.
This is usually achieved by simply plugging a cable from one
unit's output to an input on another or the same unit, using
a patchcord. The earliest synthesisers where of this type and
this is the origin of the usage "patch" to describe
the parameter settings on modern synthesisers which no longer
use this arrangement. Systems of this type where made by Moog
(series III), Roland (System 100 and 700) and Korg (MS10, 20
etc.). These systems were very flexible and led naturally to
creative experimentation, but were expensive to manufacture and
market. This resulted in a newer generation of synthesisers which
had a more or less predetermined signal path, which were often
less flexible but easier to use. There has recently been a revival
of interest in modular synthesisers and there are still manufacturers
making them.
- Monophonic
- The ability (or restriction depending on your viewpoint)
of an instrument such as a clarinet or some types of synthesiser
to play only one note at a time. Generally a monophonic synthesiser
will follow a rule to deal with any occasion when two notes appear.
It might play the most recently received (remember that in MIDI although you think you play a chord, the
notes are sent individually one after the other sufficiently
fast (usually) that you think they sound together), or it might
play the note with the highest pitch. Some MIDI controllers require
synthesisers that can work monophonically across a number of
channels, six in the case of a MIDI guitar. Thus although the
synthesiser may be polyphonic it is working monophonically on
each channel (2). If you think about it a real guitar can be
considered to be six monophonic string instruments.
- Multistage
Envelope Generator
- See Envelope Generator.
- Natural Frequency
- The frequency of vibration or oscillation
which a system (anything from a road bridge to an violin string)
will inherently adopt according to its structure given a suitable
excitation, such as a gale force wind or a bow. Also called the
normal mode.
- Noise
- A word used to describe signals which humans consider to
contain little useful information, or which they actually find
unpleasant. There are some synthetic types of noise which are useful
in sound synthesis and technical equipment alignment etc. These
are called white noise, pink noise and (the author has heard)
blue noise. White noise contains all frequencies
in equal amplitude distribution (and
the metaphor is from white light which has a similar attribute).
Pink noise is filtered white noise (some frequencies removed)
and other colours of the noise rainbow represent other filterings.
- Panning
- The process of controlling the relative position of a sound
in a stereo field during mixdown or recording using a pan-pot.
Usually this is not completely effective as the pan-pot alters
only the relative amplitude of the sound
left to right and not the crucial time aspect.
- Partial
- (1) A single frequency, sinewave
component of any sound. all sounds are composed of a number of
partials. There are two classes of partials. See also Harmonic
and Inharmonic. (2) Used confusingly
by Roland to refer to a basic sound generator in a number of
its "LA Synthesis" products, beginning with their MT32.
- Perfect Pitch
- The ability possessed by some people to describe one or more
heard pitches by their note names without error. This is sometimes
regarded as a magical ability but is no more remarkable than
the ability to name a colour, and like that skill can be learnt
by most children and even some adults. It is a rarer skill simply
because it is less practised. Some people have a more extreme
form where they can not only name the note heard but tell you
whether it is flat or sharp. Some even feel discomfort if it
incorrect. This "gift" is occasionally described as
absolute pitch. It seems to be common among children with autism.
- Phon
- A unit of apparent sound level or loudness which takes account
of the variable human sensitivity to different frequencies.
- Pitch
- Broadly speaking the musical equivalent of the technical
term "frequency", although they are not exactly synonymous.
This is usually because pitch is also used as a synonym of note
name. So one musician might ask another "What pitch is that?"
and be satisfied with the answer "A", whereas the answer
"440 Hz" would probably dismay.
- Propagation
- Movement through a material. e.g. the movement of sound waves
through air.
- Pulse Wave
- A family of geometrical waveforms typically generated by
an oscillator.
They are all rectangular in shape, i.e. the only angle
which occurs is 90° between immediate, vertical transitions
and horizontal "high" or "low" levels, but
they have any possible mark/space ratio. Square wave is a special
case of pulse wave where the mark/space ratio is 1:2. The harmonic partials present are determined
by the mark/space ratio such that the harmonics which are multiples
of the rightmost number in the ratio will be absent. Thus a pulse
wave with a mark/space ratio of 1:3 will not have the 3rd., 6th.
or 9th. etc. harmonics. Other harmonics will be present at varying
amplitudes depending on their proximity
to the "dead" or absent harmonics. When the ratio becomes
very large i.e. the pulse becomes very narrow, the timbre becomes
correspondingly thin and nasal, rather like an oboe or harpsichord.
See also Ramp Wave, Sine
Wave, Square Wave, Triangle
Wave.
- Ramp Wave
- A geometrical waveform typically generated by an oscillator.
It resembles a series of ramps placed nose to tail. It
has all possible harmonic partials (odd
and even numbered). The amplitude of
each harmonic is the reciprocal of its number in the series (i.e.
the 5th. harmonic is a 5th. the amplitude of the 1st.) It has
a very powerful and brassy timbre. It sounds the same whether
the ramp rises left to right or falls left to right. Sometimes
called sawtooth. See also See also Pulse
Wave, Sine Wave, Square
Wave, Triangle Wave.
- Reverberation
- A complex of many reflected sounds occurring in an enclosed
space such as a building or cave. The effect is often confused
with echo which, strictly, is a discrete repeat of a sound event.
Reverberation occurs to some extent in any place where a sound
can occur, but is most noticeable in very large places with many
hard reflective surfaces which are at complex angles to one another,
such as large churches etc. Most people are able to recognise
particular types or reverberation and can associate these with
imaginary rooms of varying sizes. Devices for the artificial
creation of reverberation ( sometimes called "room simulation")
have been available for some time. Initially based on electromechanical
devices such as reverb springs or reverb plates, these are now
usually digital devices. Several distinct phases are observed
in the evolution of a reverberative sound and these include pre
delay, early reflections, high & low frequency damping, decay.
- Reverberation Time
- Also call Rt60. In a reverberant
environment, this is the time a sound event will take to decrease
in amplitude by 60 dB(SPL). In general
bigger spaces will have longer Rt60 times than smaller spaces,
however there are a number of other factors to be taken into
account such as the damping effect of furniture, curtains or
even people.
- Sawtooth Wave
- See Ramp Wave.
- Sine Wave
- A geometrical waveform having a curve defined by the function
y= sin x.
In theory there are no other partials
present and it can therefore be considered as the basic component
from which (by combination) all other waveforms are made. It
is the basic building block of all sound. Sometimes used quite
incorrectly to describe pure tones irrespective of waveform.
See also See also Pulse Wave, Ramp
Wave, Square Wave, Triangle
Wave.
- Sound Wave
- See Wave.
- Spectrum
- The range of frequencies or partials of an audio signal.
- Spectrum Analyser
- A device for displaying the relative amplitudes
of a range of frequencies or partials
in an audio signal.
- Square Wave
- A geometrical waveform typically generated by an oscillator.
It is a special case of pulse wave, where the mark/space
ratio is 1:2. It has only the odd numbered (1, 3, 5, 7, etc.)
harmonic partials. The amplitude
of each harmonic is the reciprocal of its number in the series
(i.e. the 3rd. harmonic is a 3rd. the amplitude of the 1st.).
It has a buzzy but mellow timbre very similar to that of a clarinet.
See also Pulse Wave, Ramp
Wave, Sine Wave, Triangle
Wave.
- Synthesiser
- (1) An electronic device for making sounds, in which the
shape and method of construction have little effect on the nature
of the sound produced. This wide definition includes: Electronic
organs, samplers, drum machines even radio sets etc. as well
as those devices which are more immediately recognised as synthesisers.
Some devices, such as the Thérémin do owe their
sound, in part, to their construction, and may be considered
somewhat "grey" in respect of this definition. (2)
A specific case of (1) above, equipped with oscillators, filters,
amplifiers as well as modulation sources. Either with a predetermined
or more or less programmable audio and control signal path, which
can be used as a musical instrument or for sound effects. The
oscillators may include the ability to replay digital recordings
of sounds, and the whole or part of the system may be implemented
using digital or analogue technologies.
- Timbre
- The quality of a sound determined by its partial
structure, that is the relative frequencies
and amplitudes of the various sinewaves
which collectively make up that particular sound. It is more
or less synonymous with "tone". It is this quality
which allows you to distinguish between a flute and an oboe playing
the same pitch at the same volume.
- Triangle Wave
- A geometrical waveform typically generated by an oscillator.
It is triangular in shape and comprises the same sequence
of only odd numbered (1, 3, 5, 7, etc.) harmonic
partials as the square wave, but as the amplitude
of each harmonic is the reciprocal of the square of the harmonic
number (i.e. the 3rd. harmonic is a 9th. the amplitude of the
1st.), the sound is much weaker or more mellow. See also Pulse Wave, Ramp Wave,
Sine Wave, Square
Wave.
- Wave Waveform
- A cyclic propagation of energy through a medium at a constant
velocity. e. g. sound pressure waves through air, or a diagram
of such oscillations. Also refers to the appearance of the oscillating
voltage of an audio signal on an oscilloscope. See also Pulse
Wave, Ramp Wave, Sine
Wave, Square Wave, Triangle
Wave.
- Wavelength
- The distance between two identical points on a waveform i.e.
one cycle of the waveform, or the spatial distance between two
identical points of an electromagnetic or sound pressure wave
which have the same phase. In high frequency
waves, there are more cycles in a given unit of time than there
are in low frequency waves, this means they are closer together
and consequently the wavelength of a high frequency is shorter
than that of a low frequency. The wavelength of an given frequency
can be determined by dividing the speed of propagation of the
wave by its frequency. For electromagnetic waves this is c/f,
where c is the velocity of light and f is frequency, this gives
a result in metres. For sound pressure waves it is approximately
334 m/s divided by the frequency in Hz, so that audio frequencies
have wavelengths in the range from 16 metres to 1.6 centimetres.
- White Noise
- A signal which contains all possible audio frequencies
in equal average amplitudes. Useful
for testing equipment.
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Godric Wilkie
