cutmp3 is a small command line MP3 editor. It lets you select sections of an MP3 interactively or via a timetable and save them to separate files without quality loss. Silence and ID3 tag searching are also possible. For playback it uses mpg123. The program works with VBR files and files bigger than 2GB. There is also a simple frontend for it, called xcutmp3.
Beast is a powerful music composition and modular synthesis application. It offers multiple input methods like multitrack, piano roll, and pattern editing and supports skins. On the technical side, it has a wide range of abilities like sequencing, unlimited undo/redo history, real-time synthesis with multiprocessor support, full duplex 32-bit audio rendering, precise timing down to sample granularity, on demand loading of partial wave files, on the fly decoding of various sample formats, aliasing free oscillators, and full Scheme scripting support.
mkat is a set of command line tools for burning and cataloging data CD/DVD/BD and audio CDs. The catalog can later be searched for certain files or an audio CD. Tags can be used to categorize CD/DVD/BDs, e.g. comedy, drama, kids, sports. mkat is configured to use wodim/growisofs and genisoimage to do the real work, but it should be possible to configure it to use arbitrary programs.
JackMixDesk is based on JackMiniMix and is a general purpose mixer for the Jack Audio Connection Kit. It has an OSC-based control interface, and a configurable number of mono/stereo inputs and pre/post sends/outputs that can be controlled by sending it OSC messages. There is LASH support and an XML config file.
MuseScore lets you notate and compose music easily with your keyboard, your mouse, or a MIDI keyboard. You can print beautifully engraved sheet music or export it as PDF or PNG. You can play your score, transpose it, and save it as audio or MIDI file. MuseScore also supports MusicXML to let you share your composition with other scorewriters. MuseScore is often advertised as a cost effective alternative for Sibelius and Finale.
ebook2cw is a command line program that converts a plain text file (like an eBook) to Morse code (CW) MP3 or OGG files. Morse parameters like speed and tone frequency, and audio parameters such as bit rate, sample rate, and quality can be changed by command line switches. It automatically splits and numbers the output files by chapters.