MUS 570B

Basic Terms Relating to MIDI Computer Music

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ADSR--[also see ENVELOPE] Attack, Decay, Sustain, Release

AFTERTOUCH--A MIDI message generated by further pressure on a key that is already depressed--often, vibrato, or some other sound modulation.

ALIASING / FOLDOVER--Distortion caused in digital synthesis when frequencies higher than 1/2 the sample rate are created. (They fold over, or generate lower frequencies, which are usually not desirable.)

ALPHANUMERIC--Any member of the set of all numbers, letters, and other characters used by the computer (the computer keyboard).

AMPLIFIER--A device which controls the volume or loudness of a signal.

AMPLITUDE--[also see INTENSITY] Technically, amplitude is the distance between the rest position and the farthest point to which an object, such as a vibrating string, moves (displacement amplitude), or to the maximum increase of air pressure in a sound wave (pressure amplitude). Amplitude is the size of the vibration. As amplitude increases, so does the perceived volume or loudness of a sound signal.

AMPLITUDE MODULATION (AM)--A variance of the amplitude of one signal (the carrier) in accordance with the frequency and amplitude of a second signal (the program).

ANALOG-TO-DIGITAL CONVERTER (ADC)--[also see DAC] A device capable of converting an analog signal into a series of digital values representing the signal, such as a sampler.

ANALOG RECORDING--[also see DIGITAL RECORDING] Using voltages to represent acoustical vibrations which are normally recorded as a corresponding series of magnetic fluctuations on tape.

ATTACK--The initial phase of a sound.

ATTENUATOR--[also see POT] A device that controls the strength of some parameter of a signal.

AUDIO-FREQUENCY RANGE--The range of frequencies perceived by humans as sound: from roughly 16-20 Hz to 20 kHz.

CHANNEL--One track of a tape recorder; one of 16 lines of MIDI data transmission.

CHORUS EFFECT--Combining the main signal with several delayed versions of the signal. It replicates the effect of a chorus singing a single note providing a fuller sound.

CLICK TRACK--A click sound used as an aid in synchronizing material to be recorded.

CONTROLLER--A synthesizer module or function which controls some aspect of another module or function; a keyboard is a controller.

DAISY CHAIN--Connecting two or more synthesizers or other electronic devices, enabling one (the master) to control the others (slaves).

DAT RECORDER--(Digital Audio on Tape) A recorder which encodes acoustic audio signals digitally.

DECAY--A decrease in signal amplitude.

DECIBEL (dB)--A standard unit of loudness; 1/10th of a Bel (named after Alexander Graham Bell). Example: normal conversation = 60 dB; threshold of pain = 130 dB.

DEFAULT--A standard or start-up condition.

DIGITAL-TO-ANALOG CONVERTER (DAC)--[also see ADC] Used to convert digital information into analog voltages.

DIGITAL DELAY--A device that creates effects based on varying the number and amplitude of, and time between, the echoes of a signal.

DIGITAL RECORDING--[also see ANALOG RECORDING] Using numbers (digital) to represent acoustical vibrations which are measured at equal intervals of time.

DIRECT BOX--[also see PHANTOM POWER] A device which enables, for example, an electric guitar to be connected directly to a mixing console, accomplished by lowering the guitar's impedance level (to avoid electrical hum).

DISC--Storage medium for music or video information.

DISK--Computer storage medium, usually 3.5".

EDITING--Altering previously-recorded data.

EFFECTS--Echo, Chorus, Digital Delay, Reverb and other modifications produced by passing a sound or audio signal through an effects processor.

ENVELOPE--[also see ADSR] The amplitude history of a sonic event; a multi-segmented voltage curve or series of digital events and rates.

FADER--A potentiometer (pot) or slider that varies the value of some parameter or signal.

FREQUENCY--[also see PITCH] The number of cycles per unit time of a periodic waveform, usually measured in Hertz (Hz). Frequency is an acoustical property of sound and can be measured by laboratory instruments.

FREQUENCY MODULATION (FM)--A variation in the frequency of one signal caused by another, often periodic, signal. FM produces many more sidebands than AM.

GENERAL MIDI--A recent addition to the MIDI specification which ensures that a sequence created on one MIDI instrument will sound relatively the same on another. This includes a table of 128 instrument sounds grouped into families.

HARMONIC--A sine wave component of a complex waveform. Also sometimes called partial.

HERTZ (Hz)--The unit of measurement of frequency equal to one cycle of a periodic waveform per second (vibrations per second).

IMPEDANCE--Resistance to AC current, measured in ohms. Professional microphones and other studio equipment use low impedance which allows long cable runs (v. high impedance).

INTENSITY--[also see AMPLITUDE] The amount of power in a sound, which is directly related to the amplitude of the vibration. Volume and loudness are used somewhat interchangeably to indicate intensity. Intensity is normally measured in decibels, an objective laboratory measurement, whereas loudness is a subjective perception on the part of the hearer. Lower frequencies typically require an increase in intensity, or volume, to be perceived as sounding at the same intensity level as mid-range frequencies.

INTERFACE--A device or point where two or more instruments or procedures meet and communicate.

LOOP--A method of recording or playback whereby a specified number of measures repeat.

MICROCOMPUTER--Either an entire computer system on a single chip, or a small computer consisting of microprocessor and associated chips; a personal computer.

MICROPROCESSOR--The central processing unit of a microcomputer.

MIDI--Musical Instrument Digital Interface.

MIDI IN--Port which receives MIDI information from another source.

MIDI OUT--Port which transmits MIDI information to another source.

MIDI THRU--Port which retransmits MIDI information to another source; used in chaining.

MODULATION WHEEL / JOYSTICK--A manual controller normally used to regulate the amount of periodic fluctuation that can be introduced to the pitch of a tone (vibrato). May be a joystick.

MONOPHONIC--One sound. Monophonic synthesizers only allow one key on a music keyboard, or one signal path, to be active at a time.

MP3--technically, "MP3-1 Audio Layer 3," as so-dubbed by the Motion Picture Experts Group (MPEG).  The short answer is that MP3 is a file compression technique that reduces sound files to about one-tenth of their original size.  All the sounds are stored as numbers.  MP3 removes any numbers representing sounds beyond the range of human hearing.  While MP3 files aren't "exactly" the same quality as a CD audio file, they come pretty close.

MUTE--A switch or control that zeroes out or turns off the audio from a specified track.

NYQUIST THEOREM--Signals with frequencies up to a little less than half the sample rate can be sampled without distortion. That is, the sampling rate must be at least twice the number of cycles of vibration per second of the highest recorded frequency in order to accurately represent the sound without distortion.  (Also, see test three study guide.)

OVERDUB / SOUND ON SOUND--The addition of material to a track after the initial recording.

OVERWRITE--Erases previously-recorded material and substitutes the newly-recorded material.

PAN--The stereo field from left to right.

PARAMETER--A variable; some aspect or characteristic of musical time or space which may be identified and used to control or articulate the flow of music.

PATCH--The voice-name/location (bank, instrument number) of a particular synthesizer sound.

PHANTOM POWER--Power from a mixer that is obtained from the cable which connects the direct box to the mixer. If the direct box does not require power, it is called a passive direct box.

PITCH--[also see FREQUENCY] A musical term for a note or tone. Pitch is what is perceived of the frequency and is a psychoacoustical attribute.

PITCH BEND--Manual alteration of the pitch of a note through use of a pitch bend device (usually a wheel or joystick).

PLUG TYPES--Be able to recognize: phone plug (stereo or mono), phono plug (RCA), mini phone plug, 3-pin XLR/Cannon, 5-pin DIN (MIDI). (Diagrams in text.)

POLYPHONIC--Many sounds. Music keyboards which may control more than one signal path at a time.

POTENTIOMETER (POT)--[also see ATTENUATOR] A variable resistor used to control amplitude and other signal characteristics.

PPQ or PPQN--Pulses Per Quarter Note. A division of the timing resolution.

QUANTIZATION--The production of a series of discrete (separate) values, as opposed to a continuous function. As applied to rhythm, it refers to error correction with regard to attack point and/or release point.

SAMPLE--A numerical value representing a voltage. The more samples per second, the more accurately an analog signal may be digitally stored and reproduced.

SEQUENCER--A device, or software, which allows recording and playback of music keyboard information. In a MIDI environment, sequencers handle a wide range of MIDI data, and are not restricted to keyboards and note data.

SMPTE TIME CODE--Developed by the Society of Motion Picture & Television Engineers (SMPTE), this is the standard code used to synchronize sight and sound.

SPLIT POINT--The point at which the synthesizer keyboard is divided into different timbral regions. This point is adjustable.

STEP RECORDING--The sequencing of material one event at a time, with duration being specified rather than a function of real-time performance.

SYNTHESIZER--A set of electronic modules or devices used for the generation and modification of sound.

TOUCH SENSITIVITY--The ability of a MIDI keyboard or other controller to produce or respond to velocity information based on how hard or quickly keys are struck.

TRACK--A channel on a tape recorder or sequencer; one of a set of concentric circles on a floppy disk.

TWEAKING--Experimenting with a controller, a.k.a., fooling around with the knobs to adjust some parameter.

WAVE FORM--One means of describing an electrical signal or sound pressure by showing how the amplitude of the signal varies over time.

WIDGET--A knob, slider, meter, etc.

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