This " .is_audio_player " file is an implementation for mass storage devices (pendrive, portable HDD, etc ..) to mimic as a portable audio player in Linux music management softwares (Rythmbox, Banshee, Amorok, etc...). This is also a workaround for some portable audio player that are not recognizable by the Linux music management softwares as a portable audio player (mount as a mass storage device when plug-in through USB). Once the mass storage device is recognized as a portable audio player, you can use music management softwares (Rythmbox, Banshee, etc ...) to manage the music in the "portable audio player". This file have to be created in the root path of the mass storage devices. Note that this is a hidden file (files with a "dot" in front of their filenames), so remember to enable "show hidden files" option in nautilus or use "-a" option in your "ls" command to find it. Below are all the options available for this file: ...