Shorten (SHN) is a file format used for compressing audio data. It is a form of data compression of files and is used to losslessly compress CD-quality audio files (44.1 kHz 16-bit stereo PCM). Shorten is no longer developed and other lossless audio codecs such as FLAC, Monkey's Audio(APE), TTA, and WavPack (WV) have become more popular. However, Shorten is still in use by some people because there are legally traded concert recordings in circulation that are encoded as Shorten files. Shorten files use the .shn file extension.
The AVR file extension is a data format known as Audio Visual Research File. AVR files were developed for use on Apple Macintosh computers. They were specifically, used for the older 680x0-based Atari ST computer systems.