REX2 is a proprietary type of audio sample loop file format developed by Propellerhead

Propellerhead Software

Propellerhead Software is a music software company, based in Stockholm, Sweden, and founded in 1994. They are most notable for the studio emulation Reason.- History :...

, a Swedish

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 music software company.

It is one of the most popular and widely-supported loop file formats for sequencer

Music sequencer

The music sequencer is a device or computer software to record, edit, play back the music, by handling note and performance information in several forms, typically :...

 and digital audio workstation

Digital audio workstation

A digital audio workstation is an electronic system designed solely or primarily for recording, editing and playing back digital audio. DAWs were originally tape-less, microprocessor-based systems such as the Synclavier and Fairlight CMI...

 software. It is supported by PreSonus Studio One

PreSonus Studio One

PreSonus Studio One is a music creation, production and mastering application for Mac OS X and Windows made by PreSonus.-Early development:In 2006, KristalLabs Software Ltd., a start-up company founded by Wolfgang Kundrus and Matthias Juwan, began working on Studio One in cooperation with PreSonus...

, Propellerhead Reason, Steinberg Cubase, Steinberg Nuendo

Nuendo

Nuendo is a music software product developed by Steinberg for music recording, arranging, editing and post-production as part of a Digital Audio Workstation. The package is aimed at audio and video post-production market segments, but it also contains optional modules that can be used for...

, Cockos REAPER

REAPER

REAPER is a digital audio workstation created by Cockos. It is distributed with an uncrippled evaluation license with a nag screen explaining the license cost. It is currently available for Microsoft Windows and Mac OS X...

, Apple Logic

Logic Pro

Logic Pro is a hybrid 32 / 64 bit digital audio workstation and MIDI sequencer software application for the Mac OS X platform. Originally created by German software developer Emagic, Logic Pro became an Apple product when Apple bought Emagic in 2002...

, Digidesign Pro Tools

Pro Tools

Pro Tools is a digital audio workstation platform for Microsoft Windows and Mac OS X operating systems, developed and manufactured by Avid Technology. It is widely used by professionals throughout the audio industries for recording and editing in music production, film scoring, film, and television...

, Ableton Live

Ableton Live

Ableton Live is a loop-based software music sequencer and DAW for Mac OS and Windows by Ableton. The latest major release of Live, Version 8, was released in April 2009. In contrast to many other software sequencers, Live is designed to be an instrument for live performances as well as a tool for...

, Cakewalk Project5, Cakewalk Sonar

Cakewalk Sonar

Cakewalk SONAR is a digital audio workstation made by Cakewalk for recording, editing, mixing, mastering and outputting audio. The latest versions of the software are SONAR Home Studio 7, SONAR Home Studio 7 XL, SONAR X1 Producer Edition, SONAR X1 Studio Edition, SONAR X1 Essential Edition, and...

, Image-Line FL Studio

FL Studio

FL Studio is a digital audio workstation developed by the Belgian company Image-Line. FL Studio features a graphical user interface based on a pattern-based music sequencer...

, MOTU Digital Performer

Digital Performer

Digital Performer is a full-featured Digital Audio Workstation/Sequencer software package published by Mark of the Unicorn of Cambridge, Massachusetts for the Apple Macintosh platform.-Ancestry:...

, MOTU Mach 5 (software sampler), and Synapse Audio Orion Platinum

Orion Platinum

Orion is a music production suite developed by Synapse Audio Software for Microsoft Windows.The software supports all stages of music production, from composing and arranging music to mixing and mastering. Its features include multitrack audio recording, audio generation, audio effects, and a...

, among others.

REX files are named after the three-letter filename suffix for "ReCycle EXport

ReCycle (program)

ReCycle is a music loop editor designed and developed by Swedish software developers Propellerhead Software. It runs on Microsoft Windows and Apple Macintosh based PCs. The software debuted in 1994....

," as these are files generated by Propellerhead's ReCycle looping utility. The filename extension

Filename extension

A filename extension is a suffix to the name of a computer file applied to indicate the encoding of its contents or usage....

s for the file format are .rex and .rx2.

REX file format and use

REX2 loops are created in ReCycle by analyzing audio files to locate zero crossings

Zero crossing

Zero-crossing is a commonly used term in electronics, mathematics, and image processing. In mathematical terms, a "zero-crossing" is a point where the sign of a function changes Zero-crossing is a commonly used term in electronics, mathematics, and image processing. In mathematical terms, a...

 in the waveform, usually at the start of a beat

Beat (music)

The beat is the basic unit of time in music, the pulse of the mensural level . In popular use, the beat can refer to a variety of related concepts including: tempo, meter, rhythm and groove...

 or other rhythmic point. The file is then divided into "slices" delineated by these markers (a form of metadata

Metadata

The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...

). This allows compatible DAW

Digital audio workstation

A digital audio workstation is an electronic system designed solely or primarily for recording, editing and playing back digital audio. DAWs were originally tape-less, microprocessor-based systems such as the Synclavier and Fairlight CMI...

 software to adjust the playback start time of each slice, so that the loop can dynamically match the tempo of a song without altering the pitch

Pitch (music)

Pitch is an auditory perceptual property that allows the ordering of sounds on a frequency-related scale.Pitches are compared as "higher" and "lower" in the sense associated with musical melodies,...

 of the loop, as would normally happen if the audio file was slowed down or sped up. Depending on the host software, individual slices can be triggered via MIDI notes, and individually tuned up and down in pitch if desired.

Royalty Free Rex2 Loop and sample collections are now available from many sources including Prime Loops

Prime Loops

-Background: is an audio production company based in London, UK and was founded by Ben Jayakody in 2008. The company’s focus is on the development of samples, loops and software sampler patches. Products are available in multiple formats allowing compatibility with popular DAW’s such as Logic Pro,...

, Smash Up The Studio, Future Loops, Samplerbanks, original-music Loopmasters, DanceMIDIsamples, PowerFX

PowerFX

PowerFX is a small recording company, based in Stockholm, Sweden. The company has been producing music samples, loops and sound effects since 1995...

 and Mi7 Libraries.

The original REX format was mono only; REX2 supports mono or stereo

STEREO

STEREO is a solar observation mission. Two nearly identical spacecraft were launched into orbits that cause them to respectively pull farther ahead of and fall gradually behind the Earth...

 files.

The REX2 format uses a proprietary compression algorithm that can reduce the file size by up to 60%.