Glossary Of Terms, definitions of terms used in recording and in Reaper Options

[Saoirse O'Shea]

Glossary of terms



ADC – Analogue to Digital Converter
Device that changes an analogue signal to digital information.

ADSR – Attack, Decay, Sustain and Release
The four main envelop types of a soundwave that control how the amplitude of the wave develops over time. ADSR envelops can be used to control the spectral evolution of a sound by modulating the cut-off frequency of a filter.

AES/EBU
A digital signal interface based on a standard agreed by the Audio Engineering Society and the European Broadcasting Union. AES/EBU is the professional equivalent of S/PDIF.


Aliasing
Either an alternative user assigned name given to an input or output in Reaper.
OR – a type of audio distortion that occurs when a signal is sampled at too low a sampling rate to accurately capture the high frequency detail.

All-pass filter
Filtering device that delays the frequency components by different amounts and then mixes this with the original signal. Note – unlike conventional filtering no attenuation occurs.

Amplifier
Device that increases or decreases the amplitude of a signal that passes through it.

Amplitude
The depth of compression where the peak amplitude is the point of maximum displacement from the signal wavepoint’s midpoint. Amplitude contributes to perceived loudness.

Analogue
A signal that has a value at every point in time – a continuous wave.

ASIO – Audio Stream Input Output.
A protocol developed originally by Steinberg that allows software sequencers to communicate with audio devices including soundcards so that audio recording and playback can be performed. The current standard is ASIO2.

Attenuation
The reduction in amplitude of a sound signal.

Balance
Either the relative levels of two or more sound elements in a mix. OR midi controller no. 8 used to adjust the relative levels of two components of a sound.

Band-pass filter
A filter that allows a band of frequencies between two cut-off points to pass through unchanged whilst attenuating those frequencies that are above or below the chosen band.

Band-reject filter
A filter that attenuates a band of frequencies between two cut-off points whilst letting frequencies above and below the band through. Cf notch filter.

Bandwidth
Range between two frequency points within the spectrum of an audio signal

Bit – Binary digit
Smallest unit of information in binary notation – either 0 or 1.

Bit depth (sample size)
Level of detail at which a computer samples analogue audio to make a digital signal. For recording 16 and 24 bit depth are common although 24 is often preferred. Cf sampling rate.

Bit rate
Number of kilobytes per second of data in an mp3 or other audio file. Highest commonly used bit rate for audio is 320kbps. Standard bit rate for an encoded mp3 is 128kbps, which is roughly equivalent to 1 Mb of digital information per minute of audio.

Buffer
An audio driver setting that helps determine the rate at which audio passes between a computer’s processor and the sound card. Lowering the buffer size reduces the amount of latency whilst recording and/or monitoring. Increasing the buffer size can help prevent pops and clicks whilst recording. See also latency.

Bus
An internal pathway that can form part of an audio routing system. IN Reaper a track is essentially a bus when more then one other track has been routed to it.

Centre frequency
Centre point of a passband or stopband in a bandpass or band-reject filter.

Channel
A path through which an audio signal flows. Reaper is able to use 64 separate channels with any single track or tracks.

Chorus
An effect produced by passing a signal through one or more delay lines and modulating the delay times with an LFO. This makes a single signal sound like many.

Clipping
Distortion heard when a signal output is so loud that the audio signal’s peaks rise above the capabilities of the amplifier to reproduce them.

CODEC – compression/decompression
A program used to compress and decompress audio to and from different audio formats. Reaper uses the LAME codec.

Compression (audio)
A reduction in the dynamic range of an audio signal.

Compression (data)
Process for packing digital data more efficiently either for storage or transmission. Mp3s are a common compressed audio format.

Compressor
A level adjusting device that normally results in a reduced dynamic range of the original signal.

Cross modulation
Interconnection of the outputs of two oscillators to each others frequency inputs that results in a complex frequency modulated signal.

Cut-off
Frequency at which the response of a filter passes from the passband to the stop band (or vice versa) - the frequency at which the filter starts to have an effect.

DAC – Digital to Analogue Converter
Device for changing digital data to analogue.

Decibel (dB)
Unit of measurement of sound based on a logarithmic scale. 6dB gain roughly doubles the amplitude of the original signal.

Digital Audio Workstation (DAW)
Term used to describe a computer used as a recording studio.

Distortion
Non-linear audio process that adds extra, often unwanted, extra frequencies to the signal and so changes its waveform.

Dither
Audio processing technique that counteracts quantisation noise in a digital recording. Quantisation distortion occurs at very low levels if there are not enough bits to accurately convey the signal. Dithering converts the quantisation distortion into another signal and redistributes it to parts of the audio spectrum less obvious to the human ear.

Docker
In Reaper the tabbed viewing area for several Reaper functions (mixer, FX browser, undo, matrix etc) accessible via the View menu.

Dry
Audio signal to which no effects have been added. Cf Wet.

Envelope
Shape of sound’s amplitude variations over time. Same as Loudness contour. Cf ADSR.

Gain
Measure of the increase in relative amplitude between the input and output of an amplifier.

Gate
Either an audio device that attenuates the level of an input when it falls below a given threshold. Useful for filtering out unwanted background noise and interference during silent parts of a musical piece. OR the time between when a note is triggered by pressing a key on a musical instrument and when the note is ended by releasing the key.

General Midi (GM)
Addition to the midi protocol that provides a standard set of rules for patch mapping, drum and percussion note mapping, multi-timbrality, polyphony. Both Roland and Yamaha have extended form – GS (General Standard) and XG (Extended General Midi) respectively.

High Pass Filter
Filter that removes all sound below the chosen frequency. This can be useful for removing some kinds of low frequency rumble and/or hum.

Input monitoring
Process of having the audio stream being recorded fed directly back to the musician through their headphones. If latency is high a delay, or echo, might be heard.

Latency
Delay between user input and the time taken for the digital audio system to respond and process the data through its hardware and software. Usually measure in milliseconds – for input monitoring a latency of 5ms or less is usually ok.

Level
Measure of amplitude of an audio signal.

LFO – Low Frequency Oscillator
Type of oscillator that operates below human hearing often used to modulate a second oscillator to produce vibrato, tremolo and other modulation effects.

Limiter
Peak level control device used to reduce gain of an input signal when it exceeds a given threshold. Usually characterized by a fast attack time and gain reduction that acts only on the loudest peaks in a signal.

Loudness
Subjective response of the ear to the amplitude of a signal.

Loudness contour
Shape of the amplitude of a signal as it evolves over time. Same as envelope. Cf ADSR.

Low Pass Filter
Removes all sound above a given frequency. Can be used to remove hiss.

MIDI – Musical Instrument Digital Interface
Data communication standard for the exchange of musical information between electronic musical instruments and also computers.

Mp3 MPEG Audio Layer 3
Compressed audio format widely used to transfer music over the internet.

Normalisation
Effect that permanently adjusts the amplitude of audio to a given value. Can be useful to obtain a consistent level of volume for different recorded tracks.

Notch Filter
Type of band-reject filter that attenuates a very narrow band of frequencies (the notch) between two cut-off points whilst allowing the rest of the signal to pass unchanged.

Plug-in
Small program used by Reaper to manipulate a sound. Plug-ins can include effects like chorus and delay. Common formats for plug-ins include DirectX and VST (Virtual Studio).

Quantisation
Process of transforming a continuous analogue signal into a series of discrete values during ADC.

Reverb
An effect that simulates the natural reverbations of a sound that help create a sense of ambience and depth or space.

Routing
The path, or paths, taken by an audio stream which on playback takes it from the track on which it was recorded all the way through to its position in the final mix.

Routing Matrix
Overview in Reaper of the entire routing network.

Sampling Rate
Measurement of how many times per second an audio recording software captures the incoming audio signal. Common rates are 44.1 kHz, 48 kHz and 96 kHz.

Send
Method by which audio is routed from one track to another track or bus that in turn accepts it as a receive.

Stems
Groups of selected tracks and/or folders. These allow you to render selected tracks to disc at the same time –or instead of – the main mix. Stems can be used to ‘freeze’ fx on tracks, or to render each track in a mix for a mastering engineer to adjust later.

Sysex – System exclusive
Form of midi message that allows for non-standard communication between midi enabled devices. Often used for the transfer of a Manufacturer Specific System Exclusive and Universal System Exclusive data. Universal System Exclusive data includes midi Machine Code (MMC), midi Show Control, Sample Dump Standard, midi file dump and General midi On and General midi Off.

Takes
Part of an item that includes a media source (audio, midi). An item can have multiple takes that may refer to different recoded versions of a mix.

Tracks
In Reaper the horizontal bars on the Timeline and vertical bars on the Mixer. These contain multiple media items and envelopes. Tracks can be standard (items and envelopes), Folders (which contain items, envelopes and standard tracks), stems.

Track Control Panel (TCP)
Area on the left of the Reaper screen in Track View where the various tracks are listed.

VST (Virtual Studio)
Plug-in format developed by Steinberg. VSTi is VST instrument.

Wet
An audio signal to which effects have been added.


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Though it might be helpful to provide some definitions of terms used. Note - this is not complete yet - I'm still adding to it but if I've missed any you want then shout.

Cheers,
Tony


Editorial note: published 2007-11-12

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