A free multi-track audio editor and recorder
Audacity is a free, easy-to-use, multi-track audio editor and recorder for Windows, Mac OS X, GNU/Linux and other operating systems. The interface is translated into many languages. The version currently hosted here is 2.1.0 (March 2015). More recent versions than this are available from http://www.audacityteam.org/download/ . Audacity is free software, developed by a group of volunteers and distributed under the GNU General Public License (GPL). Programs like Audacity are also called open source software, because their source code is available for anyone to study or use. There are thousands of other free and open source programs, including the Firefox web browser, the LibreOffice or Apache OpenOffice office suites and entire Linux-based operating systems such as Ubuntu
Audio Tag Editor
Kid3 audio tag editor can edit the tags of MP3, Ogg, FLAC, MPC & WMA files in an efficient way, convert between ID3v1 and ID3v2, set the tags of multiple files, generate tags from file names or vice versa and import from freedb, MusicBrainz and Disco
EasyABC is an open source ABC editor
EasyABC allows the user to create, edit, view, play, convert music written in the ABC music notation language. The program was written in Python 2.7 and WxPython by Nils Liberg and runs on Windows, OSX, and Linux. Nils Liberg is no longer supporting this open source package, however I have volunteered to continue its support and development.
KurzFiler is a software for editing the files of the Kurzweil sampler series. It is mainly intended for users of these great instruments.
Mr. Random is a utility useful for filling a portable MP3 audio player with music randomly selected from a larger collection situated on a computer hard drive. Filtering and history are supported. Skinnable using SkinLF. Java 6.0 is required to run.