Glossary of Electronic Music Terms
map: A table in which input values are assigned to outputs arbitrarily by the user on an item-by-item basis.
mapper: A device that translates MIDI data from one form to another in real time.
matrix modulation: A method of connecting modulation sources to destinations in such a way that any source can be sent to any combination of destinations.
Mb: See megabyte.
MCI: Media control interface. A multimedia specification designed to provide control of onscreen movies and peripherals like CD-ROM drives.
megabyte (Mb): Linguistically speaking, a million bytes. In practice, a megabyte often contains 1,024 kilobytes.
memory: A system or device for storing information -- in the case of musical devices, information about patches, sequences, waveforms, and so on.
merger: A MIDI accessory that allows two incoming MIDI signals to be combined into one MIDI output.
MIDI: (Musical Instrument Digital Interface) A communications standard for relaying information about a sound from an application or digital musical instrument to a synthesizer chip. MIDI commands contain all the information a sound board needs to reproduce the desired sound. MIDI is a specification for the types of control signals that can be sent from one electronic music device to another.
MIDI clock: A timing reference signal sent over a MIDI cable at the rate of 24 clock pulses per quarter-note (ppq).
MIDI Mapper: A Windows applet that automatically maps (shifts the value of) channel, program change, and note numbers. For example, a map could cause all notes coming in on MIDI channel 3 to go out on MIDI channel 7.
MIDI mode: Any of the ways of responding to incoming MIDI data. While four modes -- omni off/poly, omni on/poly, omni off/mono, and omni on/mono -- are defined by the MIDI specification, omni on/mono is never used, and at least two other useful modes have been developed -- multi mode for multitimbral instruments and multi-mono for guitar synthesizers.
MIDI Out/Thru: A MIDI output port that can be configured either to transmit MIDI messages generated within the unit (Out) or to retransmit messages received at the MIDI In (Thru).
MIDI thru: There are two types of MIDI thru. One, a simple hardware connection, is found on the back panels of many synthesizers. The thru jack in this case simply duplicates whatever data is arriving at the MIDI in jack. Sequencers have a second type, called software thru. In this case, data arriving at the in jack is merged with data being played by the sequencer, and both sets of data appear in a single stream at the out (not the thru) jack. A software thru is useful because it allows you to hook a master keyboard to the sequencer's MIDI input and a tone module to its output. You can then play the keyboard and hear the tone module, and the sequencer can also send its messages directly to the tone module.
millisecond (ms): One one-thousandth (0.001) of a second.
mixer: A device that adds two or more audio signals together.
mod: (1) Modulation. (2) Modification.
modem: A device (modulator/demodulator) that allows computer information to be sent over a telephone line.
modulation: The process of sending a control signal to a sound source so as to change the character of the sound.
module: A hardware sound generator with no attached keyboard. A module can be either physically separate or integrated into a modular synthesizer, and is designed to make some particular contribution to the process of generating electronic sound.
mod wheel: A controller, normally mounted at the left end of the keyboard and played with the left hand, that is used for modulation. It is typically set up to add vibrato. See modulation, vibrato.
mono mode: One of the basic reception modes of MIDI devices. In mono mode, an instrument responds monophonically to all notes arriving over a specific MIDI channel.
monophonic: Capable of producing only one note at a time.
MPC: Multimedia Personal Computer. A specification stating the minimum hardware requirements a computer must meet to display the MPC logo. They include 2Mb of RAM, a 16MHz 386SX processor, and 8-bit sound capabilities. This specification was published in 1990, and has since been bettered by the MPC 2 spec.
MPC 2: Multimedia PC, level 2. This specification requires the same types of hardware as MPC level 1, but with increased power and capacity. For example, 4Mb of RAM, a 25MHz 486SX processor, and 16-bit sound capabilities are specified.
ms: See millisecond.
MTC: MIDI time code. MTC is a way of transmitting SMPTE timing data over a MIDI cable. See SMPTE time code.
multi mode: A MIDI reception mode in which a multitimbral module responds to MIDI input on two or more channels and maintains musical independence between the channels, typically playing a different patch on each channel.
multisample: The distribution of several related samples at different pitches across the keyboard. Multisampling can provide greater realism in sample playback (wavetable) synthesis, since the individual samples don't have to be transposed over a great distance.
multitimbral: Capable of making more than one tone color (timbre) at the same time. A typical multitimbral tone generator can play, for example, the brass, piano, and violin parts all at once.
normalize: To boost the level of a waveform to its maximum amount short of clipping (distortion). This maximizes resolution and minimizes certain types of noise.
Nyquist frequency: The highest frequency that can be reproduced accurately when a signal is digitally encoded at a given sample rate. Theoretically, the Nyquist frequency is half of the sampling rate. For example, when a digital recording uses a sampling rate of 44.1kHz, the Nyquist frequency is 22.050kHz. If a signal being sampled contains frequency components that are above the Nyquist limit, aliasing will be introduced in the digital representation of the signal unless those frequencies are filtered out prior to digital encoding. See aliasing, brick-wall filter.
omni mode: A MIDI reception mode in which a module responds to incoming MIDI channel messages no matter what their channel.
OMS: Open Music System (formerly Opcode MIDI System). A real-time MIDI operating system for Macintosh applications (and slated to be integrated into Windows 95). OMS allows communication between different MIDI programs and hardware, so that, for example, a sequencer could interface with a librarian program to display synthesizer patch names -- rather than just numbers -- in the sequencer's editing windows.
operator: A term used in Yamaha's FM synthesizers to refer to the software equivalent of an oscillator, envelope generator, and envelope-controlled amplifier.
oscillator: An electronic sound source. In an analog synthesizer, oscillators typically produce regularly repeating fluctuations in voltage; that is, they oscillate. In a digital synth, an oscillator more typically plays back a complex waveform by reading the numbers in a wavetable.
overdub: To record additional parts alongside (or merged with) previous tracks. Overdubbing enables "one-man band" productions, as multiple synchronized performances are recorded sequentially.
overtone: A whole-number multiple of the fundamental frequency of a tone. The overtones define the harmonic spectrum of a sound. See Fourier analysis, partial.
parallel interface: A connection between two pieces of hardware in which several data lines carry information at the same time. Compare with serial interface.
parameter: A user-adjustable quantity that governs some aspect of a device's performance. Normally, the settings for all of the parameters that make up a synthesizer patch can be changed by the user and stored in memory, but the parameters themselves are defined by the operating system and cannot be altered.
partial: One of the sine-wave components (the fundamental, an overtone, or a tone at some other frequency) of a complex tone. See overtone.
patch: Verb: To connect together, as the inputs and outputs of various modules, generally with patch cords. Noun: The configuration of hookups and settings that results from the process of patching, and, by extension, the sound that such a configuration creates. Often used to denote a single tone color or the contents of a memory location that contains parameter settings for such a tone color, even on an instrument that requires no physical patching.
patch map: A map with which any incoming MIDI program change message can be assigned to call up any of an instrument's patches (sounds). See map, MIDI Mapper.
PCM: Pulse code modulation -- a standard method of encoding analog audio signals in digital form.
percentage quantization: A method of quantization in which notes recorded into a sequencer with uneven rhythms are not shifted all the way to their theoretically perfect timings but instead are shifted part of the way, with the amount of shift being dependent on the user-selected percentage (quantization strength). See quantization.
physical modeling synthesis: A type of sound synthesis performed by computer
models of instruments.This technique emulates the impulse patterns of real-world
instruments using a software
pitch-bend: A shift in a note's pitch, usually in small increments, caused by the movement of a pitch-bend wheel or lever; also, the MIDI data used to create such a shift. See bend.
pitch-shift: To change the pitch of a sound without changing its duration, as opposed to pitch-transpose, which changes both. Some people use the two terms interchangeably.
plug-in: A software program that acts as an extension to a larger program, adding new features.
pole: A portion of a filter circuit. The more poles a filter has, the more abrupt its cutoff slope will be. Each pole causes a slope of 6dB per octave; typical filter configurations are two-pole (12dB/oct) and four-pole (24dB/oct). See rolloff slope.
poly mode: A MIDI reception mode in which a module responds to note messages on only one channel, and plays as many of these notes at a time (polyphonically) as it can.
polyphonic: Capable of producing more than one note at a time. All synthesizers place a limit on how many voices of polyphony are available. General MIDI-compliant synthesizers are required to provide 24 voices of polyphony. Compare with multitimbral.
polyphony: The number of voices (notes) a device can produce simultaneously.
poly pressure: Polyphonic pressure. (Also called key pressure.) A type of MIDI channel message in which each key senses and transmits pressure data independently. Compare with channel pressure.
port: Verb: To translate a program written for one computer so that it can be
run on a different model. Noun: An electrical connector of some specialized type, e.g., SCSI port, MIDI port, serial port.
portamento: See glide.
pot: Potentiometer. A device (commonly attached to a knob or slider) used to adjust some aspect of the signal being passed through it, or to send out a control signal corresponding to its position.
ppq: Pulses per quarter-note; the usual measure of a sequencer's clock resolution.
preset: (1) A factory-programmed patch that cannot be altered by the user. (2) Any patch. Note: Some manufacturers make distinctions between presets, programs, and/or patches, each of which may contain a different set of parameters.
pressure sensitivity: See aftertouch, channel pressure, poly pressure.
program: Verb: To create a synthesizer patch. Noun: A patch. See patch, preset.
program change: A MIDI message that causes a synthesizer or other device to switch to a new program (also called preset, patch) contained in its memory.
programmable: Equipped with software that enables the user to create new sounds or other assignments by altering parameter settings and storing the new settings in memory. An individual control parameter is said to be programmable if its setting can be stored separately with each individual patch.
quantization: A function found on sequencers and drum machines that causes notes played at odd times to be "rounded off" to regular rhythmic values. See percentage quantization.
quantization noise: One of the types of error introduced into an analog audio signal by encoding it in digital form. The digital equivalent of tape hiss, quantization noise is caused by the small differences between the actual amplitudes of the points being sampled and the bit resolution of the analog-to-digital converter.
quantized: Set up to produce an output in discrete steps.
QuickTime: A software multimedia environment developed by Apple Computer, running on the Macintosh or under Windows 3.1. QuickTime enables the creation and playback of QuickTime movies featuring full-motion video, MIDI tracks and 16-bit ADPCM audio.
RAM: Random access memory. RAM is used for storing user-programmed patch parameter settings in synthesizers, and sample waveforms in samplers. A constant source of power (usually a long-lasting battery) is required for RAM to maintain its contents when power is switched off. Compare with ROM.
real time: Occurring at the same time as other, usually human, activities. In real-time sequence recording, timing information is encoded along with the note data by analyzing the timing of the input. In real-time editing, changes in parameter settings can be heard immediately, without the need to play a new note or wait for computational processes to be completed.
reconstruction filter: A lowpass filter on the output of a digital-to-analog converter that smoothes the staircase-like changes in voltage produced by the converter in order to eliminate clock noise from the output.
release: The portion of an envelope that begins after the key is lifted. See ADSR.
release velocity: The speed with which a key is raised, and the type of MIDI data used to encode that speed. Release velocity sensing is rare but found on some instruments. It is usually used to control the rate of the release segments of the envelope(s).
resolution: The fineness of the divisions into which a sensing or encoding system is divided. The higher the resolution, the more accurate the digital representation of the original signal will be.
resonance: A function on a filter in which a narrow band of frequencies (the resonant peak) becomes relatively more prominent. If the resonant peak is high enough, the filter will begin to oscillate, producing an audio output even in the absence of input. Filter resonance is also known as emphasis and Q. It is also referred to in some older instruments as regeneration or feedback, because feedback was used in the circuit to produce a resonant peak.
reverb: A type of digital signal processing that produces a continuous wash of echoing sound, simulating an acoustic space such as a concert hall. Reverberation contains the some frequency components as the sound being processed, but no discrete echoes. See echo, DSP.
ring modulator: A special type of mixer that accepts two signals as audio inputs and produces their sum and difference tones at its output, but does not pass on the frequencies found in the original signals themselves. See clangorous.
rolloff slope: The acuity of a filter's cutoff frequency. Rolloff is generally measured in decibels (dB) per octave. A shallow slope, such as 6dB per octave, allows some frequency components beyond the cutoff frequency to be heard, but at a reduced volume. When the rolloff slope is steep (on the order of 24dB per octave), frequency components very close to the cutoff frequency are reduced in volume so much that they fall below the threshold of audibility. See filter, pole.
ROM: Read-only memory. A type of data storage whose contents cannot be altered by the user. An instrument's operating system, and in some cases its waveforms and factory presets, are stored in ROM. Compare with RAM.
sample: Noun: A digitally recorded representation of a sound. Also, a single word of the data that makes up such a recording. See word. Verb: To make a digital recording. See sampling.
sample-and-hold: A circuit on an analog synthesizer that, when triggered (usually by a clock pulse), looks at (samples) the voltage at its input and then passes this voltage on to its output unchanged, regardless of what the input voltage does in the meantime (the hold period), until the next trigger is received. In one familiar application, the input was a noise source and the output was connected to oscillator pitch, which caused the pitch to change in a random staircase pattern. The sample-and-hold effect is often emulated by digital synthesizers through an LFO waveshape called "random."
sampler: An instrument that records and plays back samples, usually by allowing them to be distributed across a keyboard and played back at various pitches.
sampling: The process of encoding an analog signal in digital form by reading (sampling) its level at precisely spaced intervals of time. See sample, sampling rate.
sampling rate: The number of samples taken per second. Typical sampling rates vary from 11kHz to 48kHz. See sampling, Nyquist frequency.
scrub: To move backward and forward through an audio waveform under manual control, in order to find a precise point in the wave for editing purposes.
SCSI: Small Computer Systems Interface, a high-speed communications protocol that allows computers, samplers, and disk drives to communicate with one another. Pronounced "scuzzy."
SDII: Sound Designer II, an audio file format. The native format of Digidesign's Sound Designer II (Macintosh) graphic audio waveform editing program.
SDS: The MIDI sample dump standard. SDS is used to transfer digital audio samples from one instrument to another over a MIDI cable.
sequence: A set of music performance commands (notes and controller data) stored in a sequencer.
sequencer: A device or program that records and plays back user-determined sets of music performance commands, usually in the form of MIDI data. Most sequencers also allow the data to be edited in various ways, and stored on disk.
serial interface: An electronic connection between two devices in which digital data is transferred one bit after another, rather than several bits at a time. MIDI is a serial interface. Compare with parallel interface.
SFI: A file extension specifying Turtle Beach's SoundStage audio format. Typically encountered as FILENAME.SFI.
sidebands: Frequency components outside the natural harmonic series, generally introduced to the tone by using an audio-range wave for modulation. See clangorous.
single-step mode: A method of loading events (such as notes) into memory one event at a time. Also called step mode and step-time. Compare with real time.
sine wave: A signal put out by an oscillator in which the voltage or equivalent rises and falls smoothly and symmetrically, following the trigonometric formula for the sine function. Sub-audio sine waves are used to modulate other waveforms to produce vibrato and tremolo. Audio-range sine waves contain only the fundamental frequency, with no overtones, and thus can form the building blocks for more complex sounds.
SMDI: SCSI musical data interchange. A specification for sending MIDI sample dumps over the SCSI bus. See SDS.
SMP: Turtle Beach's SampleVision audio file format. Typically encountered as FILENAME.SMP.
SMPTE time code: A timing reference signal developed by the Society of Motion Picture & Television Engineers and used for synchronizing film and videotape to audio tape and software-based playback systems. Pronounced "simp-tee." See frame.
SND: Sound resource. A Macintosh audio file format.
snapshot automation: A form of mixing automation (frequently MIDI-controlled) in which the controlling device records the instantaneous settings (the snapshot) for all levels and pan pots, and recalls these settings on cue.
song position pointer (SPP): A type of MIDI data that tells a device how many sixteenth-notes have passed since the beginning of a song. An SPP message is generally sent in conjunction with a continue message in order to start playback from the middle of a song.
sostenuto pedal: A pedal found on the grand piano and mimicked on some synthesizers, with which notes are sustained only if they are already being held on the keyboard at the moment when the pedal is pressed. Compare with sustain pedal.
soundcard: A circuit board that installs inside a computer (typically an IBM-compatible) adding new sound capabilities. These capabilities can include an FM or wavetable synthesizer and audio inputs and outputs. MIDI inputs and outputs are also normally included.
split keyboard: A single keyboard divided electronically to act as if it were two or more separate ones. The output of each note range is routed into a separate signal path in the keyboard's internal sound-producing circuitry, or transmitted over one or more separate MIDI channels. Applications include playing a bass sound with the left hand while playing a piano sound with the right.
SPP: See song position pointer.
status byte: A MIDI byte that defines the meaning of the data bytes that follow it. MIDI status bytes always begin with a 1 (hex 8 through F), while data bytes always begin with a 0 (hex 0 through 7).
step input: In sequencing, a technique that allows you to enter notes one step at a time. (Also called step recording.) Common step values are sixteenth- and eighth-notes. After each entry, the sequencer's clock (position in the sequence) will advance one step, then stop, awaiting new input. Recording while the clock is running is called real-time input.
subtractive synthesis: The technique of arriving at a desired tone color by filtering waveforms rich in harmonics. Subtractive synthesis is the type generally used on analog synthesizers. Compare with FM synthesis, sampling.
sustain: The third of the four segments in an ADSR envelope. The sustain portion of the envelope begins when the attack and decay portions have run their course, and continues until the key is released. The sustain control is used to determine the level at which the envelope will remain. While the attack, decay, and release controls are rate or time controls, the sustain control is a level control.
sustain pedal: The electronic equivalent of a piano's damper pedal. In most synthesizers, the sustain pedal latches the envelopes of any currently playing or subsequently played notes at their sustain levels, even if the keys are lifted.
sync: Synchronization. Two devices are said to be in sync when they are locked together with respect to time, so that the events generated by each of them will always fall into predicable time relationships.
sync track: A timing reference signal recorded onto tape. See SMPTE time code, FSK.
synthesizer: A musical instrument that generates sound electronically and is designed according to certain principles developed by Robert Moog and others in the 1960s. A synthesizer is distinguished from an electronic piano or electronic organ by the fact that its sounds can be programmed by the user, and from a sampler by the fact that the sampler allows the user to make digital recordings of external sound sources.
system-common: A type of MIDI data used to control certain aspects of the operation of the entire MIDI system. System-common messages include song position pointer, song select, tune request, and end-of-system-exclusive.
system-exclusive (sys-ex): A type of MIDI data that allows messages to be sent over a MIDI cable that will be responded to only by devices of a specific type. Sys-ex data is used most commonly for sending patch parameter data to and from an editor/librarian program.
system real-time: A type of MIDI data that is used for timing reference. Because of its timing-critical nature, a system real-time byte can be inserted into the middle of any multi-byte MIDI message. System real-time messages include MIDI clock, start, stop, continue, active sensing, and system reset.
THD: Total harmonic distortion. An audio measurement specification used to determine the accuracy with which a device can reproduce an input signal at its output. THD describes the cumulative level of the harmonic overtones that the device being tested adds to an input sine wave. THD+n is a specification that includes both harmonic distortion of the sine wave and nonharmonic noise.
timbre: (1) Tone color. (2) One of the building blocks of a patch in a Roland synthesizer. Pronounced "tam-br."
time code: A type of signal that contains information about location in time. Used for a synchronization reference when synchronizing two or more machines such as sequencers, drum machines, and tape decks.
touch-sensitive: Equipped with a sensing mechanism that responds to variations in key velocity or pressure by sending out a corresponding control signal. See velocity, aftertouch.
track: Verb: To be controlled by or follow in some proportional relationship (as when a filter's cutoff frequency tracks the keyboard, moving up or down depending on what note is played). Noun: One of a number of independent memory areas in o sequencer. By analogy with tape tracks, sequencer tracks are normally longitudinal with respect to time and play back in sync with other tracks.
transient: Any of the non-sustaining, non-periodic frequency components of a sound, usually of brief duration and higher amplitude than the sustaining components, and occurring near the onset of the sound (attack transients).
tremolo: A periodic change in amplitude, usually controlled by an LFO, with a periodicity of less than 20Hz. Compare with vibrato.
upload: to transfer a file from a computer to an electronic bulletin board (BBS), usually via modem. See download.
VCA: Voltage-controlled amplifier. A device that responds to a change in voltage at its control input by altering the gain of a signal being passed through it. Also, the digital equivalent of a VCA.
VCF: Voltage-controlled filter. A filter whose cutoff frequency can be changed by altering the amount of voltage being sent to its control input. Also, the digital equivalent of a VCF.
VCO: Voltage-controlled oscillator. An oscillator whose frequency can be changed by altering the amount of voltage being sent to its control input.
velocity: A type of MIDI data (range 1 to 127) usually used to indicate how quickly a key was pushed down (attack velocity) or allowed to rise (release velocity). Note: A note-on message with a velocity value of 0 is equivalent to a note-off message.
velocity curve: A map that translates incoming velocity values into other velocities in order to alter the feel or response of a keyboard or tone module.
velocity sensitivity: A type of touch sensitivity in which the keyboard measures how fast each key is descending. Compare with pressure sensitivity.
vibrato: A periodic change in frequency, often controlled by an LFO, with a periodicity of less than 20Hz. Compare with tremolo.
virtual: Existing only in software.
VOC: A file extension specifying the Creative Labs Sound Blaster audio format. Typically encountered as FILENAME.VOC.
voice: (1) An element of synthesizer circuitry capable of producing a note. The polyphonic capability of a synthesizer is defined by how many voices it has. See polyphony. (2) In Yamaha synthesizers, a patch (sound).
voice channel: A signal path containing (at a minimum) an oscillator and VCA or their digital equivalent, and capable of producing a note. On a typical synthesizer, two or more voice channels, each with its own waveform and parameter settings, can be combined to form a single note.
voice stealing: A process in which a synthesizer that is being required to play more notes than it has available voices switches off some currently sounding voices (typically those that have been sounding longest or are at the lowest amplitude) in order to assign them to play new notes.
.WAV: The Windows audio file format. Typically encountered as FILENAME.WAV.
waveform: A signal, either sampled (digitally recorded) or periodic, being generated by an oscillator. Also, the graphic representation of this signal, as on a computer screen. Each waveform has its own unique harmonic content. See oscillator.
waveshape: See waveform.
wavetable synthesis: A common method for generating sound electronically on a synthesizer or PC. Output is produced using a table of sound samples--actual recorded sounds--that are digitized and played back as needed. By continuously rereading samples and looping them together at different pitches, highly complex tones can be generated from a minimum of stored data without overtaxing the processor.
wavetable lookup: The process of reading the numbers in a wavetable (not necessarily in linear order from beginning to end) and sending them to a voice channel.
wet: Consisting entirely of processed sound. The output of an effects device is 100% wet when only the output of the processor itself is being heard, with none of the dry (unprocessed) signal. Compare with dry.
wheel: A controller, normally mounted at the left end of the keyboard and played with the left hand, that is used for pitch-bending or modulation.
word: A single number (sample word) that represents the instantaneous amplitude of a sampled sound at a particular moment in time. In 8-bit recording, a sample word contains one byte; in 16-bit recording, each word is a two-byte number.
workstation: A synthesizer or sampler in which several of the tasks usually associated with electronic music production, such as sequencing, effects processing, rhythm programming, and data storage on disk, can all be performed by components found within a single physical device.
zero crossing: A point at which a digitally encoded waveform crosses the center of its amplitude range.
zone: A contiguous set of keys on the keyboard. Typically, a single sound or MIDI channel is assigned to a given zone.