17. Glossary of Terms


Advanced Audio Coding (AAC) is a patented audio compression algorithm which uses a form of lossy data compression. Designed to be the successor to MP3, AAC generally achieves better sound quality at similar bit rates. While the .aac extension is sometimes used for AAC-encoded files, they are typically saved with an .m4a file extension.


An acoustic fingerprint system built entirely on open-source technology. It aims to create a free database of user-submitted audio fingerprints with mapping to the MusicBrainz metadata database and provide a web service for audio file identification using this database. For more information, see`<https://acoustid.org/>`_.


Short for Audio Interchange File Format. High-quality digital audio file format, similar to .wav files. Contains CD-quality audio stored in a non-compressed, lossless format. AIFF files generally end with a .aiff or .aif extension.


Apple Lossless Audio Codec (ALAC) is a lossless audio file format used by iTunes and other Apple products. ALAC files use the same MP4 container format as AAC and use the same file extensions (m4a, mp4). Mixxx and many other programs are not compatible with ALAC. It is recommended to convert ALAC files to FLAC for use in Mixxx.


An Application Program Interface (API) is a specification and set of rules for how software programs interact with each other. In Mixxx, an example of this is the Sound API that Mixxx uses to communicate with the operating system to make use of the soundcards connected to the computer.

audio interface

An audio interface is a device that facilitates the input and output of audio signals to and from a computer, typically connected by USB. Almost all computers come with a basic audio interface built in, but a higher quality audio interface with at least 4 output channels is recommended for Mixxx.


A balance control on a mixer allows you to adjust the balance between the left and right channel. The balance refers to the relative volume of the corresponding channel in a stereo audio signal.


In musical notation, a bar (or measure) is a segment of time defined by a given number of beats. Typically, a piece consists of several bars of the same length.


A series of markers that point to the location of beats within the track. Beatgrids are used for advanced mixing functions such as track sync, precise effects synchronization, looping and accurate BPM representation.


A mixing technique used to establish a similar tempo with two or more tracks, making them sound like just one track.


Files that contain compiled computer code, which was compiled from source code. Source code, which is usually a bunch of text files, is processed with a program called a compiler. The compiler then generates a binary, which is something like an an .exe or a .dll file. By using binaries you are relieved of the task of having to compile the code by yourself.


Describe the quality of an audio or video file. For audio data the bitrate is commonly measured in kbps. For example, an MP3 audio file that is compressed at 192 Kbps will have a greater dynamic range and may sound slightly more clear than the same audio file compressed at 128 Kbps.


Beats per minute (BPM) is used as a measure of tempo in music. If you tap your foot to music you are following the “beat”. If you count how many taps you do in a minute you have calculated the BPM.

bug report

Every software has bugs. When you come across a bug in this software, you should submit a report about it to the developers. They can use this to identify, replicate and fix the issue.


CDJ is a term originally used to describe a line of CD players from Pioneer Electronics. Today CDJ generally refers to DJ CD players that work like a record player. They allow analog control of music using CDs, usually using a touch sensitive emulated vinyl control surface.


Short for compressor/decompressor, a codec is any technology for compressing and decompressing audio and video data. Some popular codecs for computer audio include MP3 and Ogg Vorbis.


An external hardware device that generates and transmits signals to a computer, usually via USB, to control software with physical controls other than a mouse and keyboard. Controllers have many uses for music such as controlling DJ programs like Mixxx. They typically send MIDI signals but some controllers use HID signals. Many DJs prefer to control DJ software using physical knobs, faders, and wheels on controllers instead of using a computer keyboard and mouse.


The crossfader is a slider that determines how much each deck of audio contributes to the master output.


A Cue or Cue point is a reference point in the track usually placed on the position the DJ wants the track to start at by default. This is useful to instantly jump to that point without seeking through the track.

cue sheet

A cue sheet (or CUE file, CUE sheet, etc.) is a formatted plain text file which is used to provide index information for a large audio file. For example, it can be used to tell software extra details about the layout of a CD to burn.


Headphone cueing, or just cueing, is listening to the next track you would like to mix in your headphones. The audience will not hear what you are cueing in your headphones. Being able to cue is a crucial aspect to DJing.


A digital audio workstation (DAW) is an electronic device or application software used for recording, editing and producing audio files.


Short for decibels. A Decibel is a logarithmic measurement of sound level. Whispering is around 25 dB while unbearable sound such as a jet engine is around 160 db. Rule of thumb: A volume increase of 10 dB is perceived as twice as loud.


A deck is like a virtual vinyl turntable. You can load a track into it and play the track, just like you would put a record on turntable and play it.

direct monitoring

A feature of many soundcards that allows microphones and other input signals to be heard through the soundcard outputs with no perceivable latency. With direct monitoring, the audio interface mixes the input signal in hardware with the output signal from Mixxx. This bypasses the latency of sending the signal into the computer for Mixxx to process and sending it back out to the soundcard.


Digital Rights Management (DRM) technologies attempt to control what you can and can’t do with the media and hardware you’ve purchased. Typically, a DRM system either encrypts the data so that it can only be accessed in a way authorized by copyright holders or marks content with a digital watermark or similar method so that the content can not be freely distributed. For information about how you can get involved in activism against DRM, see Defective by Design.


An equalizer allows the sound in specified frequency bands to be amplified or reduced, in order to adjust the quality and character of the sound.

A simple graphic equalizer consists of multiple controls for boosting or cutting bands or frequencies of sound.

A parametric equalizer controls more parameters of the sound than a graphic equalizer. It can control three aspects of each frequency: level (boost or cut), the center or primary frequency, and the bandwidth or range of each frequency.


To cause something to advance at quicker than normal speed. In terms of audio software that means if you press the fast-forward button the audio will play with increased speed as long as the button is pressed. This is useful to seek through a track.


The opposite of fast-forward. If you press the fast-rewind button the audio will play in reverse with increased speed as long as the button is pressed.

file manager

A computer program that organizes data files into groups and shows you where they are when you need to find them again. Popular file managers for the operating systems Mixxx supports are Explorer on Windows, Finder on macOS and Nautilus on GNU/Linux.


Free Lossless Audio Compression (FLAC), a patent-free audio compression similar to MP3 but lossless (i.e. there is no loss in audio quality when used). FLAC files generally end with a .flac extension.


A flanger is an effect that mixes the input signal with a delayed copy of itself which leads to interferences in the signal and creates a comb-filter effect. By routing the output of the effect back into the input (feedback), the effect is enhanced.


Short for “Graphical User Interface” and is pronounced “gooey”. It refers to a user interface based on graphics (icons, pictures and menus) instead of text. In Mixxx, it uses a mouse, keyboard, or MIDI / HID controllers as input devices.

head/mix button

The head/mix button is used to control how much you mix the master output into your headphone output. This can be very useful when cueing a track, because you can test out how it sounds when mixed with the main mix in your headphones, before letting the audience hear the track.

headphone button

The headphone button is used to indicate whether or not you are pre-listening to a deck or sampler in your headphones.

headphone output

The headphone output is what you hear in your headphones.


Short for Human Interface Device, a part of the USB specification. It specifies a device class (a type of computer hardware) for human interface devices such as keyboards, mice, game controllers, and some DJ controllers.


Similar to the main cue point, a hotcue is a reference point in the track. DJs usually place hotcues at distinctive positions within a track such as drops, breaks or kicks and snares. Mixxx supports up to 36 hotcues.


HSV stands for hue, saturation, and value, and is also often called HSB (B for brightness). The HSV Color Model represents color in a way more suited to the human perception of color. For example, the relationships “stronger than”, “darker than”, and “the opposite of” are easily expressed in HSV. In contrast, the representation of the hardware-oriented RGB model is close to what most monitors show.


Icecast is free and open-source software that allows digital audio content to be broadcast to and from media player software, enabling the creation of Internet radio stations. Unlike Shoutcast, the software provides the ability to stream in free file formats like Ogg Vorbis and run your own directory server.


Internet Relay Chat (IRC) is an online chat network. The Mixxx IRC channel was on the FreeNode IRC Network in the #mixxx channel. The channel was replaced in 2018 by the Mixxx Zulip Chat.


Short for kilobits per second. Here used to measure the quality of audio data. See bitrate


Short for ”musical key” (i.e. C major).

key lock

With key lock enabled, the tempo of the track will change but the pitch remains consistent. When unlocked, the pitch slider will speed up (or slow down) the track and the pitch will increase (or decrease) along with it.

kill switch

A button to turn on and off individual frequency ranges within a channel, i.e. treble, mid and bass. Useful for effects where the DJ drops a track out for a period or creates room for a transition.


Linux Audio Developer’s Simple Plugin API (LADSPA) is a standard for handling audio filters and audio signal processing effects.


LAME is a free software codec used to encode/compress audio into the lossy MP3 file format.


Latency refers to a short period of delay (usually measured in milliseconds) between when an audio signal enters and when it emerges from a system. Being able to lower the latency as much as possible makes a huge difference in responsiveness.

level meter

The level meter is used to show the average levels of audio signals. The level should average around the top of the green region, with the loudest parts of the music (the transients) briefly going into the yellow region. If the level meter is in the red, the signal is clipping and the gain should be turned down.


Used when describing audio compression algorithms, a lossless algorithm is one which results in no loss in audio quality when used.


Used when describing audio compression algorithms, a lossy algorithm is one which results in a loss in audio quality when used.


macOS (originally named ”Mac OS X” until 2012 and then ”OS X” until 2016) is the current Mac operating system that officially succeeded the classic Mac OS in 2001.

master output

The master output is the main audio output. It is what your audience hears.

master sync

Master sync mode persistently adjusts a track’s tempo and phase (if quantization is enabled) in order to stay in sync with other decks that are in master sync mode.


In general, any piece of information about a music file that Mixxx uses (e.g. title, artist, album, hotcue locations, loops, etc.). Various file metadata formats allow information such as the title, artist, album, and track number to be stored in the audio file itself, see https://en.wikipedia.org/wiki/ID3 . Mixxx stores additional metadata about music files in its database, like beatgrid, waveform data, hotcues, playlists, crates, number of plays, etc.


Short for Musical Instrument Digital Interface. A digital communications language and hardware specification enabling compatible electronic instruments, sequencers, computers, etc., to communicate with each other in a network. Most DJ controllers use MIDI to communicate with computers.


A patented audio compression algorithm which uses a form of lossy data compression. It is de-facto standard of digital audio compression for music. MP3 files generally end with a .mp3 extension.


A open-source music encyclopedia that collects music metadata and makes it available to the public. For more information, see https://musicbrainz.org/.

Ogg Vorbis

A patent-free audio compression algorithm which uses a form of lossy data compression. It is designed to provide for efficient streaming and manipulation of high quality digital audio. Ogg Vorbis files generally end with a .ogg or .oga extension.


Generically, open-source refers to a program for which the source code is available to the public for use and/or modification from its original design free of charge. Open source code is typically created as a collaborative effort in which programmers improve upon the code and share the changes within the community. Open source sprouted in the technological community as a response to proprietary software owned by corporations. For more information, see Wikipedia.


An operating system feature used to draw hardware-accelerated graphics. Mixxx uses OpenGL to draw the waveform displays and spinning vinyl widgets.

operating system

Your operating system (OS) is the computing environment on your computer. For example, Windows, macOS, or GNU/Linux are the three operating systems that Mixxx supports.


Opus is a totally open, royalty-free, highly versatile lossy audio codec. The .opus filename extension is recommended.


PFL or “pre-fader listen” is the headphone signal that is not affected by the deck volume faders. This allows for pre-listening tracks in headphones by lowering the volume fader so the deck plays only to headphones but not to the audience. See also: headphone button.


The phase of a track is its position relative to another track. If two tracks are sync’d to the same tempo and in-phase then they should be playing so that their beats are aligned.

pitch bend

A technique used by DJs that temporarily bends the rate of a track up or down, usually while a button is held. This technique is usually used to make micro-adjustments to the synchronization of tracks while beatmatching. Before digital DJing, this was accomplished by dragging one’s finger alongside the turntable to slow it down or by twisting the record spindle to speed it up.


A podcast is a feed of audio or video files made available for free or for purchase over the Internet. Podcast clients such as iTunes allow listeners to subscribe to the feed and automatically download content to their portable audio players as it becomes available.


Quantization is the process of aligning notes and other events like loops or cuepoints so that they start or finish exactly on beats or fractions of beats.

ramping pitch bend

Basically identical to the regular pitch bend with the difference that the pitch changes gradually, instead of all at once. Often uses for temporary pitch changes. It simulates the effect of touching a turntable to temporarily slow down or speed up a record.


The speed at which a track is played back, usually expressed in terms of a percentage of the speed relative to the tracks normal rate. Often while mixing, DJs adjust the rates of tracks so that they can play at the same tempo as other tracks. This allows DJs to beatmix, and is an essential part of DJing.

ReplayGain (toiston voimakkuuden tasoitus)

ReplayGain normalizes audio data in a non-destructive way, so the tracks in your music library don’t all play at different volumes. Audio files are scanned by a psychoacoustic algorithm to determine the loudness of the audio data. ReplayGain information is stored as metadata in a digital audio file in order for the sound to be correctly played at the right level of loudness.


Reverse plays a track backwards.


The RGB color model is an additive color model in which red, green, and blue light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three additive primary colors, red, green, and blue.


Shortcuts let you work more efficiently. This manual shows some shortcuts for accessing Mixxx functions with an English keyboard layout. Depending on your language settings the defaults may be different.


Shoutcast is proprietary software that allows digital audio content to be broadcast to and from media player software, enabling the creation of Internet radio stations.


Another name for an audio interface, although few audio interfaces are shaped like cards anymore.


Sync allows you to automatically adjust a track’s tempo and phase to be in sync with another deck that is playing.


The speed of a track measured in BPM.


Used here in conjunction with vinyl control. A special audio signal on a control vinyl or control CD (timecode media) that a computer can listen to in order to determine speed, direction and position of the playback.


A track is another word for a song.


Uniform Resource Locator. The address that defines the route to a file on an Internet server. URLs are typed into a Web browser to access Web pages and files, and URLs are embedded within the pages themselves as hypertext links. One example of a URL is https://mixxx.org .

vinyl control

A method of controlling DJ applications which simulates the traditional DJing paradigm of two turntables. Using special timecode media, the DJ application analyzes the timecode signal and simulates the sound and feel of having your music collection on vinyl.


A term that refers to the degree of sound intensity or audibility; loudness. Volume is determined by people’s perception and does not directly correspond to any physical property of sound.


Standard digital audio file format used for storing waveform data; allows audio recordings to be saved with different sampling rates and bitrates; often saved in a 44.1 KHz, 16-bit, stereo format, which is the standard format used for CD audio. Wave files are not compressed, and are therefore lossless. Wave files generally end with a .wav extension.

waveform overview

The waveform overview shows the waveform envelope of the entire track, and is useful because they allow DJs to see breakdowns far in advance.

waveform summary

The waveform summary shows the waveform envelope of the track near the current playback position.


Zulip is a powerful, open source group chat application that combines the immediacy of real-time chat with the productivity benefits of threaded conversations. The Mixxx Zulip Chat at can be found at https://mixxx.zulipchat.com .