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SFX
Machine Online Documentation
GLOSSARY
additive synthesis
A method of sound synthesis based on adding
sine waves in a
harmonic series (e.g., 100 Hz, 200 Hz, 300 Hz, etc.)
The Hammond
B3 organ implemented additive synthesis by allowing
the user to
adjust "drawbars." In SFX Machine, you
can use the sliders to
mix sine waves in various proportions.
aliasing
A type of distortion caused by sampling at too
low a sample rate.
To avoid aliasing, the sample rate must be at least
twice the
highest frequency in the sound.
AM
See Amplitude
Modulation.
amplitude
Amplitude refers to the relative height of a
waveform. A sound's
loudness is a function of its amplitude.
Amplitude
Modulation
A modulation method in which the amplitude of
one wave (the
carrier)
is controlled by the amplitude of another wave (the
modulator).
Unlike Ring Modulation, Amplitude Modulation uses
a modulator that is unipolar (i.e., always positive).
In SFX
Machine, the AM modulator is automatically converted
to a
unipolar signal.
Low-frequency AM results in volume control or tremolo
effects.
Modulator frequencies that are themselves in the
audio range
result in sum and difference sideband tones that
were not
necessarily present in either the carrier or the
modulator.
artifact
An unintended side-effect of a technological
process.
ASCTM
Our proprietary Advanced Sound CreationTM
technology;
marketing-speak for the Edit Screen.
bandpass
A bandpass filter passes an area around the
specified cutoff
frequency and rolls off (attenuates) frequencies
to either side.
bipolar
A bipolar signal is one that goes above and
below zero. Most
audio signals are bipolar.
carrier
An audio signal controlled by another signal
(the modulator).
The term is usually applied to AM and FM synthesis.
Category
In SFX Machine, Categories are folders of Preset
files. You can
select a Category (for example, "Delay")
by using the Category
List Box; then choose a Preset ("Sitar Drone")
from the Preset
List Box.
channel
An audio signal pathway. SFX Machine uses a
maximum of two
channels, Left and Right.
chorus
An effect that makes a single voice sound like
multiple voices in
unison. You can implement chorusing by sending a
sound through a
series of delays whose delay times are slowly being
modulated.
clipping
An amplitude distortion that occurs when signal
levels try to
exceed the available amplitude range. The tops and
bottoms of
clipped waveforms are typically squared off, generating
frequencies that weren't in the original signal.
comb
filter
A filter whose frequency response exhibits a
series of deep
peaks or notches equally spaced in frequency (hence
the word
"comb").
In SFX Machine, you can implement a comb filter by
delaying the
source signal by at least 0.1 ms and adding it (with
either a
positive or negative output amplitude) to the original
signal.
Alternatively, instead of adding in the delayed input,
you can
delay and scale the output (the sum of the source
and the delayed
and scaled source) and feed that back to the input,
producing a
stronger resonance effect.
cutoff
frequency
For lowpass and highpass filters, the cutoff
frequency specifies
the dividing line between frequencies that get passed
by the
filter and frequencies that get attenuated (rolled
off). For
bandpass filters, the cutoff specifies the center
frequency of
the band that gets passed.
cycle
One complete repetition or oscillation of a
waveform.
Frequencies are commonly measured in cycles per second.
dB (decibel)
A common unit for measuring audio levels. It
uses a logarithmic
scale, which roughly corresponds to how the ear hears
differences in amplitude.
DC offset
DC stands for "Direct Current." A
signal whose midpoint is
skewed away from zero is said to have a DC offset;
this can
result in clicks or other problems. You can use the
DC Offset
process in SFX Machine to negate a pre-existing offset.
delay
A basic DSP process, the output of which is
the input signal
delayed by a specified time (called the delay time).
You can use
delays to create filters, echoes, flangers, feedback
loops and
many other DSP effects.
delay
time
A parameter that specifies the interval between
when a sample
enters the delay and when it comes out the other
end.
depth
See modulation depth.
destination
The destination, also known as the "target"
module, is a module
that is being modulated by another module. Select
the
destination by using the Dest pop-up menu.
Think of the Dest menu as a virtual patch cord from
the
modulator to the appropriate field in the destination
module.
distortion
Any process that distorts the shape and frequency
content of a
waveform. Types of distortion include clipping, waveshaping,
and
SFX Machine's Raise-to-Power and PhaseShaping processes.
Doppler
effect
A pitch shift that occurs when a sound source
and a listener are
moving closer together or further apart. Modulating
a Delay Time
in SFX Machine shrinks or stretches the waveforms,
producing a
pitch shift that is analogous to the Doppler effect.
downsampling
Resampling a digital signal at a lower sampling
rate. If
downsampling is not preceded by lowpass filtering,
aliasing
distortion can result.
DSP
Digital Signal Processing. Digital samples and
analog voltages
are both abstract representations of sound; digital
signals are
simply a different type of analogy, in which the
signals are
quantized both in time and amplitude and are represented
by a
series of numbers.
Echo
1. A mountain nymph who could only repeat the
last words
spoken by another. Hopelessly in love with Narcissus,
she faded
away until only her voice remained.
2. Repetition of a sound due to the reflection of
sound waves. In
SFX Machine, you can create echoes by delaying a
signal and
mixing a portion of the result back into the delay's
source.
Edit
Screen
The screen that gives you direct access to all
of the pop-up
menus and parameters that define a patch.
envelope
A curve that follows some characteristic of
a sound. For
example, an amplitude envelope is a curve that follows
the
contour of a sound's amplitude.
envelope
follower
A process which "listens" to a sound
and tracks its amplitude
envelope. You can use the resulting signal to control
various
other effects, such as vibrato rate and depth, so
that the effects
intensify as the sound gets louder.
feedback
An effect that occurs when the output of a DSP
process is fed
back into the input. Interesting effects can result
when you
delay a signal, feed it through a non-linear process
such as a
filter or power distortion, and route it back to
the input. See
feedback
loop.
feedback
loop
The feedback loop is a central principle of
cybernetics, from the
flush toilet to the steam engine. Any system that
functions by
talking to itself incorporates a feedback loop.
Positive feedback loops result in a snowball effect,
with the
signal being re-amplified each time through. Negative
feedback
loops, such as thermostats, adjust themselves to
achieve a self-
regulating balance.
Multiple signals can modulate each other, resulting
in "circular
causality" or "strange loops." Each
signal becomes both cause
and effect. Together, they give rise to a self-organizing
system
with emergent properties.
See
Kevin Kelly's excellent book, Out of Control.
See Ouroborus.
field
See value entry field.
filter
A process that modifies a sound by passing some
frequencies
more readily than others, changing the spectral balance
of the
sound.
filter
frequency
See cutoff frequency.
flanging
An effect that occurs when a signal is mixed
with a delayed copy
of the signal, while the delay time continually changes.
You can
hear this effect when a jet plane passes overhead,
because the
direct sound is being mixed with the delayed reflection
from the
ground, and the relative delay time changes with
the angle of the
plane. A flanger may be thought of as a swept comb
filter.
The first musical use of flanging involved mixing
the outputs of
two tape recorders while pressing the flange of one
to slow it
down. You can implement flanging in SFX Machine by
delaying a
signal, modulating the delay with a sine wave, and
mixing in
some of the original sound.
FM
See Frequency
Modulation.
formant
A peak in the frequency response of a vocal
tract or musical
instrument. Different vowel sounds are characterized
by the
position and shape of their formants. The human vocal
tract
typically has five formant regions.
frequency
The repetition rate of a sound, typically measured
in cycles per
second. A sound's pitch is related to its frequency.
Frequency
Modulation
A modulation method in which the frequency of
one wave (the
carrier)
is controlled by the amplitude of another wave (the
modulator).
Low-frequency FM results in vibrato. Modulator frequencies
that
are themselves in the audio range result in the generation
of
sideband tones that are not necessarily present in
either the
carrier or the modulator.
frequency
response
The frequency response of a system is a curve
showing how well
the system passes various frequencies. A filter is
characterized
by the shape of its frequency response. Good audio
systems have
a flat frequency response in the audible range of
20 to 20,000
Hertz.
glissando
A smooth slide through a series of adjacent
pitches.
harmonic
A single frequency component of a sound. Also
called "overtone,"
or "partial." The timbre, or tone color,
of a sound may be
characterized by its harmonic content. A 100 Hz sound
that is
high in harmonic content (for example, a sawtooth
wave) will
have harmonics at 200 Hz, 300 Hz, 400 Hz, etc.
Hertz (Hz)
Cycles per second. A 60-Hertz hum has 60 repetitions
of its
waveform every second.
highpass
A highpass filter passes the frequencies above
the specified
cutoff and rolls off (attenuates) the lower frequencies.
hold
time
The time interval during which a sample-and-hold
holds the
current sample before getting a new one.
host
program
The host program is the program that SFX Machine
plugs into; for
example, Peak, Deck or Premiere.
inharmonic
Frequency components are said to be inharmonic
if they occur at
frequencies that are not integer multiples of the
fundamental, or
base frequency.
Stretched strings, notably piano strings, produce
sounds that are
slightly inharmonic because the higher partials are
somewhat
sharp. FM and other techniques can produce extremely
inharmonic
sounds.
initial
phase
In SFX Machine, initial phase is the phase angle
(the point in the
cycle) at which a waveform begins.
Often it is best to specify an initial phase of 0º;
this helps avoid
initial clicks, since the sine of 0º is a zero-crossing.
link
A user-configurable connection that allows you
to change the
contents of a value entry field on the Edit Screen
by using one of
the sliders on the Slider Screen.
LFO
A Low-Frequency Oscillator, generally used for
adding vibrato or
tremolo or otherwise controlling an audio signal.
"Low-
frequency" implies frequencies below the audio
range (20 Hz --
20 kHz), i.e., frequencies low enough that they aren't
heard as a
tone.
lowpass
A lowpass filter passes the frequencies below
the specified
cutoff and rolls off (attenuates) the higher frequencies.
master
link
A master link is the first field linked to a
slider with multiple
links. Changing the value of the master link may
also change the
values of the associated slave links by a similar
proportion.
master
volume
A slider that controls the overall level of
a mix. In SFX Machine,
create a master volume slider by linking all the
left and right
output amplitude fields to a single slider.
mix
In SFX Machine, mix modulation (or mixing) is
simply a way of
routing the output amplitude of one module into the
input of
another.
A module's source signal is mixed (averaged) together
with any
incoming mix signals, then modulated by any incoming
amplitude
or ring modulations, before entering the specified
process.
modular
synthesis
A flexible sound synthesis method in which sounds
are produced
and modified by a number of independent signal processing
modules, which can be patched together to modulate
each other
and interact in various ways. The original modular
synthesizers
were analog voltage-controlled devices connected
by patch
cords.
modulation
The control of some aspect of a signal, for
example its
amplitude or frequency, by another signal.
modulation
amplitude
The percentage by which a signal is scaled before
it is used to
modulate another signal. If the modulation amplitude
is 100%,
the modulating signal is unchanged; its full range
is used to
control the destination signal. Also called "modulation
depth."
Increasing the modulation depth will cause a "deeper"
vibrato,
tremolo, etc.
modulation
depth
See modulation
amplitude.
Modulation
Modulation
Modulation Modulation lets a signal modulate
the depth of
another modulation. For example, the depth of a Frequency
Modulation could itself be modulated by another module
using
Modulation Modulation.
modulator
A signal that modulates or controls another
signal (the
carrier).
module
An independent unit that generates or modifies
an audio signal.
Modules can be interconnected in various ways.
monaural
(mono)
A sound with only one channel, as opposed to
stereo.
Pressing the Mono Preview button will cause SFX Machine
to
preview a stereo sound using only the left channel.
monophonic
A single melodic line without accompaniment;
for example, solo
voice.
noise
1. A complex sound made up of a broad spectrum
of non-
harmonically-related frequencies.
2. Any euphony-impaired sound, often arbitrarily
discriminated
against on aesthetic grounds.
oscillator
A signal source that produces a specified waveform
at a
specified frequency.
Ouroborus
Jungian archetype symbolizing feedback. Originally
appeared in
Egyptian art of a snake consuming its own tail; more
recently
reflected in Apple Computer's street address, 1 Infinite
Loop.
See feedback.
overflow
Overflow, or clipping, happens when a waveform
exceeds the
maximum signal level. In SFX Machine, the mix (or
average) of
the outputs on a given channel will clip if it exceeds
100% (0
dB). Excessive amounts of modulation, excessive output
levels,
and filtering with high Q values can lead to overflow.
Pan
1. Goatlike Greek god after whom panpipes were
named.
2. Parameter used to control the left/right (panoramic)
movement of a sound.
parallel
processing
A method of computation in which multiple processing
modules
operate in parallel, simultaneously controlling each
other by
sending signals back and forth. The early electronic
modular
synths may be viewed as analog parallel processing
computers.
parameter
A numerical value used to control some aspect
of an SFX Machine
patch.
patch
A configuration of interconnected modules and
associated menu
items and parameters. You can design new Patches
using the Edit
Screen. Patches are also referred to as "Presets."
phase
1. The periodically changing appearance of the
moon, due to
angular rotation.
2. A fraction of a cycle of a waveform. Typically
phase is
measured as an angle. A sine wave makes a positive
zero-
crossing at 0º phase; hits 100% at 90º
(or 1/4 cycle); makes a
negative zero-crossing at 180º (1/2 cycle);
hits -100% at 270º
(3/4 cycle); and returns to zero at 360º. See
Initial Phase.
PhaseShape
The PhaseShape process changes the shape of
sine, triangle,
square and sawtooth waveforms, thus changing their
timbres.
PhaseShape Modulation (Phase Mod) changes the amount
of
PhaseShaping over time.
pitch
A psychoacoustic phenomenon that is closely
related to but not
synonymous with frequency. Pitch is the subjective
property
that lets us compare whether one sound seems "higher"
or
"lower"
than another.
The pitch of a sound can be ambiguous or ill-defined.
What is the
pitch of a chord, a click, white noise or silence?
pitch
tracker
A process which "listens" to a sound
and attempts to track its
pitch contour. You may use the resulting signal to
modulate
another module's source frequency, filter cutoff,
or (inverse)
delay time.
polyphonic
Music in which several melodic voices are playing
at once.
power
SFX Machine's Raise to Power process distorts
the shape of a
signal by raising it to a power (exponentiating it,
or multiplying
it by itself a fractional number of times). This
results in a
distorted sound with additional harmonic content.
Preset
A file containing all the settings used by an
effect in SFX
Machine. The term also refers to the file in which
a Preset is
saved.
process
In SFX Machine, a process is a DSP algorithm
that either
modifies a sound (e.g., delay, lowpass) or extracts
information
from it (Envelope Follower, Pitch Tracker). The output
of the
process is sent to the modulation block as well as
to the left and
right outputs, if selected.
Do not confuse a DSP process with the Process button,
which
tells SFX Machine to process the audio and send it
back to the
host program.
Q
A parameter that controls a filter's roll-off
slope and the
(inverse) width of its resonant peak.
For a bandpass filter, the Q is the ratio of the
filter's center
frequency to its bandwidth. For example, if the filter's
cutoff
frequency is 500 Hz and its bandwidth is 50 Hz, its
Q is 10.
In SFX Machine, a Q of 1 results in a roll-off of
12 dB/octave for
the lowpass and highpass filters, and 6 dB/octave
on either side
for the bandpass filter. Higher Q values result in
higher slopes
and place a sharp resonant peak at the cutoff frequency.
quantization
The process of limiting a value to one of a
discrete number of
values; for example, representing an audio sample
as a 16-bit
integer. Sampling also involves quantizing time,
by sampling at
discrete intervals.
random
A random sample is one whose value does not
appear to depend
on the previous sample's value, or on anything else.
A series of
random samples sounds like white noise.
resonance
A spectral peak in the response of a filter,
the body of a musical
instrument, etc. If an external disturbance (for
example, an
earthquake) happens to match the resonant frequency
of an
object (for example, a house), the resulting vibration
can be
greatly amplified.
SFX Machine uses resonant filters, which have a peak
near the
cutoff frequency. Increasing the Q makes the peak
higher and
narrower.
Ring
Modulation
A form of modulation in which two bipolar signals
are multiplied
together. The modulator and carrier frequencies disappear
and
are replaced by tones at the sum and difference of
their
frequencies.
If the modulator's frequency is below 20 Hz, the
result is a
tremolo effect. If the modulator's frequency is itself
in the
audible range, the result is a curious change in
timbre. As the
modulator frequency increases from 0 Hz, you can
hear the
resulting signal splitting into two frequency components,
which
gradually move away from each other.
sample
A number representing the amplitude of a signal
at a given
instant in time.
sample-and-hold
A sample-and-hold samples a signal at a specified
time interval.
It holds the output at that level until the end of
the hold time
and then grabs another sample. This process is also
called
downsampling.
sample
rate
Sample rate describes how frequently an analog
audio signal is
sampled as it is converted into a series of numbers.
44.1 kHz is the standard sample rate for compact
disks; 48 kHz
is often used with digital audio tape (DAT) recording;
22.050 kHz
is frequently used for games and multimedia.
A higher sample rate allows a higher frequency response.
In
order to accurately reconstruct a sound, the sample
rate must be
at least twice the highest frequency in the sound.
sampling
Sampling, or analog-to-digital conversion, is
the process of
converting an analog signal to a series of digital
samples
(numbers).
sawtooth
wave
A waveform consisting of a periodic ramp. Its
frequency
spectrum includes all of the odd and even harmonics.
selection
The original audio source signal that is selected
in the host
application before invoking SFX Machine. Various
host programs
may refer to a selection as a region, a track, a
clip, etc.
SFX Machine may or may not pay any attention to the
original
audio signal, depending on which items are selected
in the
Source pop-up menus.
semitone
The interval between two adjacent notes on a
piano keyboard.
One semitone equals 100 cents.
sideband
An additional frequency produced as a result
of a modulation. AM,
FM and Ring Modulation can all generate sidebands
that are not
necessarily present in either of the original signals.
signal
A symbolic representation of a sound; an electrical
current or
series of numbers used to signify acoustic vibrations.
"Signal"
can also refer to "control voltages" or
modulations, electronic
messages that may or may not themselves be audible.
The beauty of modular synthesis is the way that sounds
and
modulations can both be expressed as signals and
can, therefore,
be used interchangeably, modulating things they have
no business
modulating.
signal-to-noise
ratio
A measurement of the amplitude of the desired
sound as
compared to the background noise level. In SFX Machine,
you can
improve the signal-to-noise ratio by increasing the
output
amplitude levels as far as possible without clipping;
a master
volume slider can be useful for this purpose.
sine
wave
A smooth waveform whose spectrum consists of
a single
frequency. A sine wave has a pure flute-like tone.
slave
A slave link is a field that is linked to a
master field and its
associated slider. The first link selected is the
"master;" all
other links to the same slider are the "slaves."
A slave link is
designated by a prime (apostrophe) after the link
letter (for
example, B').
Changing the value of the master link allows the
user to change
the values of the associated slave links by a similar
proportion.
Changing the value of a slave link will change the
ratio between
the slave link and the other links of that slider.
slider
link
See link.
slider
mapping
The process of linking a slider to one or more
value entry fields
on the Edit Screen.
source
As used in SFX Machine, source can refer to
the original sound
selection, or to any signal selected by the module's
Source menu.
The term can also refer to a modulation source, a
signal used to
modulate a destination module.
spectrum
By analogy with the example of light, which
can be split into its
constituent colors, an audio spectrum is the representation
of a
sound's harmonic content in terms of its component
frequencies.
square
wave
A rectangular waveform that alternates between
a positive
value and a negative value. Its frequency spectrum
includes all
of the odd harmonics and has higher harmonic content
than a
triangle wave.
stereo
Stereophonic; having two audio channels.
threshold
The Envelope Follower's threshold is an amplitude
level used to
gate the Envelope Follower's output. All amplitude
envelope
values below the specified threshold percentage will
be greatly
attenuated; amplitude envelope values above the threshold
will
be unchanged.
Generally the threshold is set to 0%, making it inactive.
timbre
A sound's tone color, which is a function of
its harmonic content.
time
constant
The Envelope Follower's time constant is used
to specify how
quickly the output tracks variations in the source
signal's
amplitude. A time constant of 20 ms means that half
of the
information used in calculating the current Envelope
Follower
value comes from the last 20 ms, and half comes from
all
previous samples.
Selection of the optimal time constant is a tradeoff.
Short time
constants are responsive but rough; long time constants
are
smooth but sluggish.
tremolo
A low-frequency variation in a sound's amplitude
envelope. In
SFX Machine, you can create tremolo by amplitude
modulating a
sound with a sine or triangle wave in the 5 to 9
Hz range.
triangle
wave
A waveform with alternating positive- and negative-sloped
ramps. Its frequency spectrum includes all of the
odd harmonics.
triggered
wah
A wah-wah filter whose cutoff frequency opens
and closes in
response to the signal's amplitude envelope.
unipolar
A unipolar signal is one that is always positive
(or always
negative), never crossing through the zero level.
In SFX Machine,
a sine wave processed with a DC Offset of 100% would
be a
unipolar signal.
value
entry field
A box that allows you to enter a numerical value.
In SFX Machine,
all values may be entered as floating point numbers,
though the
decimal point is not required.
vibrato
A low-frequency variation in a sound's frequency
envelope. In
SFX Machine, you can simulate vibrato by delay modulating
a
sound with a sine wave in the 5 to 9 Hz range. (If
the carrier is a
sine / triangle / square / saw waveform, you can
generate
vibrato by using Frequency Modulation.)
wah-wah
A variable bandpass filter which produces an
effect similar to
that of a trumpet mute. It goes "wah."
In SFX Machine, a wah-
wah can be simulated by modulating the cutoff frequency
of a
bandpass filter with a moderate Q.
white
noise
By analogy with white light (composed of equal
amounts of all
visible light frequencies), white noise is a sound
composed of an
equal mix of all audible frequencies.
zero-crossing
A point at which a waveform changes sign by
crossing the zero-
amplitude axis.
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