Other Applications
A named pipe can also be seen as a loopback on file system level: While Unix domain sockets and network sockets are using two connected files for Inter-process communication, a named pipe consists of only one file.
The audio systems OSS, ALSA and PulseAudio have also loopback modules for recording the audio output of applications and testing purposes. Unlike physical loopbacks, there is no double analogue/digital conversion and no disruption due to hardware malfunctions.
Read more about this topic: Loopback