KMidimon monitors events coming from a MIDI external port or application via the ALSA sequencer, or Standard MIDI Files. It is especially useful if you want to debug MIDI software or your MIDI setup. It features a nice graphical user interface, customizable event filters and sequencer parameters, support for all MIDI messages and some ALSA messages, MIDI playback, and saving the recorded event list to a text file or SMF.
annoyme is a program that plays a sound effect every time you hit a key on your keyboard to give you the feeling you are using a real typewriter. This can be used to impress colleagues with your typing skills or just for sentimental reasons. It supports various sound input methods, as well as multiple output libraries like ALSA or AO. Most importantly, it is also possible to add more sound themes. Currently, only input for XEvIE (on an X Server) is supported.
RMP allows remote control over playing your music files on a Linux computer. The music can be controlled via a Web interface, a smart cellphone, iPhone, Blackberry, or through a command line shell interface. If you like the song, you can download it to your phone. It supports next, searching, and volume control.
PigeBox is a complete solution to record continuous (24/7/365) audio content. It provides a bootable GNU/Linux system with all required software components to achieve the storage, the recording, and the extraction of audio content. It has been designed to provide a "plug & record" solution for radio broadcasters.
Desfonema Sequencer is a tracker-inspired MIDI sequencer. It uses a pattern oriented design, with n tracks by pattern. It offers a piano roll editor for tracks, and a tabbed track interface for patterns. It features convenient keyboard shortcuts, a virtual keyboard, step and live editing, MIDI input (ALSA), and a text-based file format that is easy to edit manually or merge and better suited for version systems like Subversion.
hexter is a software synthesizer that models the sound generation of a Yamaha DX7 synthesizer. It can easily load most DX7 patch bank files, edit those patches via a built-in editor or MIDI sys-ex messages, and recreate the sound of the DX7 with greater accuracy than any previous open source emulation (that the author is aware of). It operates as a plugin for the DSSI Soft Synth Interface.