Different types of audio file formats

Audio File Formats

Apple Loops

Apple Loops are a tagged form of AIFF audio file, which allow for easy categorisation of the files, as well as including enhanced abilities to pitch map and time stretch the audio. Although called Apple Loops, the apple loop format actually supports loops, phrases and single-hits.

The ability to categoirise the Apple Loops files becomes a handy feature, when they are included into a compatible hosting environment, such as Logic Pro X or GarageBand. When Apple Loops are added into Logic Pro X, the loop browser integrates all available files into one handy searchable location, which can be quickly filtered by Instrument / style:

Logic Pro X - Apple Loop Browser

All major music hosts/DAWs include an audio browser, with varying included features, but all will allow for you to audition the audio files and then simply import the files into your music project.

For further information on host compatibility with Apple Loops, please consult your host documentation.

Further ReadingHow to include Apple Loops into Logic Pro

Acid Wav Loops

Acid Loops are specialized music clips. They were originally created for use with Acid, the loop-based, music-sequencing software, created by Sonic Foundry in 1998.

"Acidized" loops contain tempo and key information, so that Acid and other programs that can read the "acidization" can properly time stretch and pitch shift them. Although the phrase "ACID loops" technically only refers to loops which have been "acidized", some people use the term to refer to loops in general, even when used with other software packages.


REX is the native file format of ReCycle. A REX file contains the original audio of the loop, the spces you have appped in ReCycle, and any effects or processing you have added in ReCycle. Saving an audio file as a REX file also reduces the size of the file significally. This is achieved by applying a "nonlossy" compression algorithm to the file when saved, meaning that it does not compromise the audio quality in any way.

Practically all major music software titles support the REX format. Be it music production software like Logic, Pro Tools, Cubase, Sonar, Live and of course Reason, or software instruments such as Native Instruments Kontakt, Spectrasonics Stylus RMX or Digidesign Transfuser. Check your software for more compatibility details.

CDA Audio

The audio CD format is typically referred to as a CDA file (.cda). CDA files can only be played from a CD and the files must be converted to WAV or MP3 files for storage on a computer hard disc or DVD disc. The CDA format is an industry standard (referred to as the Red Book audio standard) that is used for encoding music on CDs and audio CDs bought in the high street will use this format. CD audio uses a sample rate of 44.1 kHz and for stereo audio this requires 176,400 bytes per second (or 1,411,200 bits per second - there are 8 bits per byte) of data storage. This equates to about 10.09MB per minute of audio in CDA format.


For more information on using lossy and lossless file compression, please see our knowledge base article here.