ADSR: Attack, Decay, Sustain, and Release. Basic parameters of a synth envelope generator.

Aliasing: Unwanted frequencies which are produced when a sound is sampled at a rate which is less than twice the frequency of the highest frequency component in the sound.

Amplitude: Amount of a signal. Volume in an audio signal.

Amplitude Modulation: A change in the level of a signal. i.e. a Voltage Controlled Amplifier (VCA)  modulated by a Low Frequency Oscillator (LFO).

Analog: Data (signal) presented in a non-digital, continuous form.

Analog Synthesizer: A synthesizer which uses voltage controlled modules to synthesize sound. The three main voltage controlled modules are: Voltage Controlled Oscillator (VCO), Voltage Controlled Filter (VCF), and Voltage Controlled Amplifier (VCA).

Attack: The first parameter of an envelope generator which determines the rate or time it will take for the event to reach the highest level before starting to decay.

Audible Range: The range of frequencies that the human ear can hear. A healthy human ear can usually hear 20-20,000 Hz.

Baud Rate: The speed at which digital information is passed through a serial interface.  MIDI data is transmitted at 31.25 KBaud (31,250 bits per second).

Byte: A computer word made up of eight bits of data.

Channel, MIDI: An information path through which MIDI information is sent. MIDI provides for 16 available channels, each of which can address one MIDI instrument.

Chorus: A voice doubling effect created by layering two identical sounds with a slight delay and slightly modulating the frequency.

Click track: Metronome audio clicks that are generated by electronic devices to indicate the tempo.

Clock: A pulse from a generator for synchronizing sequencers, drum machines, etc. Common sequencer timing clock rates are 24, 48, or 96 pulses-per-quarter note. MIDI timing clocks run at a rate of 24 ppqn.

Continuous Controller: Midi information other than notes, i.e.  volume, pitch bending, modulation (vibrato).

Crossfade: To gradually fade out one sound while fading in another.

Cutoff Frequency: The frequency above which a low pass filter will start attenuating signals at its input. Abbreviated Fc.

Decibel (dB): A reference for the measurement of sound energy.

Digital to Analog Converter (DAC): A device which interprets Digital information and converts it to Analog form.

Dynamic Range: The range of the softest to the loudest sound that can be produced by an instrument.

Envelope Generator: A circuit that generates a changing voltage with respect to time. This voltage typically controls a VDF or VDA.

Equalizer: A device which allows attenuation or emphasis of selected frequencies in the audio spectrum.

Fast Fourier Transform: An algorithm which derives the Fourier spectrum from a sound file.  The mathematical method used to convert a waveform to the Frequency Domain.  Fast Fourier Transform (FFT) is used to perform spectral analysis.

Filter: A device used to remove frequencies from an audio signal and altering its harmonic structure. Low Pass filters allow frequencies below the cutoff frequency to pass (Low Pass). High Pass filters only allow the high frequencies to pass.  Band Pass filters only allow frequencies in a selected band to pass through. A Notch filter cuts frequencies that fall within its notch.

Flange: An effect created by layering two identical sounds with a slight delay (1- 20 mS) and slightly modulating the delay of one or both of the sounds.

Fourier Spectrum: The description of a sound in terms of energy versus frequency rather than its amplitude versus time (waveform).

Frequency: The number of cycles of a waveform occurring in a second.

Fundamental: The lowest note of a harmonic series. The Fundamental frequency determines a sound's overall pitch.

Ground Loop: Hum caused by currents circulating through the ground side of a piece of equipment or system.

Harmonic Distortion: The presence of harmonics in the output signal which were not present in the input signal.

LFO: Low Frequency Oscillator. An oscillator used for modulation whose range is below the audible range (20 Hz).

Low Pass Filter: A filter whose frequency response remains flat up to a certain frequency, then rolls off (attenuates signals appearing at its input) above this point.

Musical Instrument Digital Interface (MIDI): A digital communications language/protocol that allows electronic instruments, controllers, computers and other related devices to communicate. MIDI is a serial interface, which is transmitted at the rate of 31.25 KBaud or 31,250 bits per second.

MIDI Clock: Enables instruments interconnected via MIDI to be synchronized. The MIDI Clock runs at a rate of 24 pulses-per-quarter- note.

MIDI Continuous Controller: Continuously changing information such as pitch wheel or breath controller information to be passed over the MIDI line.

PWH = Pitch Wheel
CHP = Pressure
1 = Modulation Wheel
2 = Breath Controller
4 = Foot Pedal
5 = Portamento Time
6 = Data Entry
7 = Volume
8 = Balance
10 = Pan
11 = Expression Controller
16-19 = General purpose controllers 1-4
64 = Sustain Switch (on/off)
65 = Portamento Switch (on/off)
66 = Sustenuto (chord hold)
67 = Soft Pedal (on/off)
69 = Hold Pedal 2 (on/off)
80-83 = General purpose controllers 5-8
91 = External Effects Depth
92 = Tremolo Depth
93 = Chorus Depth
94 = Detune
95 = Phaser Depth
96 = Data Increment

MIDI filter: A device, processor that allows specific MIDI messages or range of messages to be recognized or ignored.

MIDI implementation chart: A standard information of the MIDI capabilities that are supported by a specific MIDI device.

MIDI in: MIDI messages from an external source.

MIDI interface: A device used to translate the serial message data of MIDI into a data structure that can be directly communicated to and from a computer.

MIDI mapper: A device, processor, used to reassign the scaler value of a data byte to another assigned value.

MIDI messages: A group of related 8-bit words, which are used to convey a series of performance or control instructions to MIDI devices within a system.

MIDI out: This port is used to transmit MIDI messages from a single source.

MIDI thru: This port provides an exact copy of the incoming data at the MIDI in port and transmits this data to another MIDI instrument or device that follows within the MIDI chain.

MIDI time code (MTC): Translating SMPTE time code into an equivalent time code that conforms to the MIDI 1.0 Specification.

Modulation: The process of one audio or control voltage source influencing a sound processor or other control voltage source.

Normalize: A digital processing function that increases the amplitude of a sound file until the peak amplitude of its loudest sample reaches 100% of full scale.

Overload: Distortion which is caused by exceeding the dynamic range of a circuit.

Pan: Moving an audio signal left or right in the stereo spectrum.

Parallel Interface: A computer interface in which data is passed simultaneously over many wires. A Parallel Interface is usually much faster than a serial interface. The SCSI Interface is an example of a Parallel Interface.

Patch: A synthesizer sound which is stored in it's computer memory. Usually refers to a sound which can be edited.

Quantization: A function of a sequencer to correct human-performance timing errors within a composition.

Sampler: A synthesizer which derives it's sounds from recording actual sounds (instruments or non musical sounds) and then storing them in computer memory.

Sampling: The process of recording a sound into digital memory.

SCSI: Acronym for Small Computer Serial Interface.

SMPTE: Acronym for Society of Motion Picture and Television Engineers who adopted a standard time code in order to synchronize video and audio.

Song Pointer: MIDI information which allows equipment to remain in sync even if the master device has been fast forwarded.

Subtractive Synthesis: The process of constructing a sound by starting with a complex sound and then removing harmonics with a filter. A low pass filter is most commonly used.

Synthesizer: A device that creates sounds electronically through the use of voltage controlled amplifiers and filters.

Timbre: Tone color. The quality of a sound.

Tone Module: A synthesizer without a piano keyboard.

Tremolo: A cyclic change in amplitude, usually in the range of 6 to 15Hz. Usually achieved by routing a LFO.

VCA: Voltage Controlled Amplifier.

VCF: Voltage Controlled Filter.

VDF: Variable Digital Filter.

VDA: Variable Digital Amplifier.

Velocity Sensitivity: A keyboard which can respond to the speed at which a key is depressed.

Vibrato: A cyclic change in pitch, usually in the range of 6 to 15Hz.

Volatile Memory: (Sometimes a state of a student’s mind or) memory which loses its data when power is removed.

Wind Controller: Woodwind-like or brass-like instrument in it's fingering, blown into triggers sounds from a tone module.

Zero Crossing: The point where the polarity of a signal passes through zero. A zero crossing provides a convenient point to splice two sounds.