LinuxBand is a GUI front-end for MMA (Musical MIDI Accompaniment). Type in the chords, choose the groove, and LinuxBand will play a musical accompaniment for you. It’s an open source alternative to Band-in-a-Box featuring: an easy to use graphical interface, an open and well-documented data format, and output to JACK MIDI to facilitate co-operation with other audio applications.
DR14 T.meter is a commandline tool for computing the Dynamic Range of your music according to the procedure used in the offline meter released by the Pleasurize Music Foundation. It is very useful to measure how loud your music is and to understand that a good quality album always has a good dynamic. It's also useful for understanding the effects of the so-called loudness war.
Auralquiz is a simple music quiz game that uses your own music files. It plays short pieces of music files from your folders and presents a question and several answers about the current song. The faster the answer, the more points you receive. Up to eight people can play in a turn-based mode. In the highest difficulty level, instead of having the buttons, the player must type the answer. Symbols like "!", "-", "." etc are filtered out, and it's not case sensitive, so it's a little easier to answer correctly.
robonobo is social music sharing and downloading software. It allows you to share your friends' music libraries and playlists, stream the audio instantly, and download the file in the background so you can burn it, export it to your music player, or do whatever you want with it. You can import your friends list and share links to your playlists via Facebook and Twitter.