SFX Machine Online Documentation

GLOSSARY
additive synthesis envelope modulation amplitude sample-and-hold
aliasing envelope follower modulation depth sample rate
AM feedback Modulation Modulation sampling
amplitude feedback loop modulator sawtooth wave
Amplitude Modulation field module selection
artifact filter monaural semitone
ASC filter frequency monophonic sideband
bandpass flanging noise signal
bipolar FM oscillator signal-to-noise ratio
carrier formant Ouroborus sinewave
Category frequency overflow slave
channel Frequency Modulation Pan slider link
chorus frequency response parallel processing slider mapping
clipping glissando parameter source
comb filter harmonic patch spectrum
cutoff frequency Hertz phase square wave
cycle highpass PhaseShape stereo
dB (Decibel) hold time pitch threshold
DC offset host program pitch tracker timbre
delay inharmonic polyphonic time constant
delay time initial phase power tremolo
depth link Preset triangle wave
destination LFO process triggered wah
distortion lowpass Q unipolar
Doppler effect master link quantization value entry field
downsampling master volume random vibrato
DSP mix resonance wah-wah
Echo modular synthesis Ring Modulation white noise
Edit Screen modulation sample zero crossing


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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