wx12Ton helps one to work with music involving twelve-note series. In particular, it displays the 48 forms of a twelve-note series, and tests series for tonal phrases. In addition, wx12Ton allows the user to list the complete set of all twelve-note series which satisfy certain criteria.
songanalysis analyzes a song in WAV, Ogg Vorbis, or MP3 format and produces an output consisting of the volume differential, the relative strength in each frequency band, and the tempo. This is useful if you want to build something that lets you find out whether you have duplicate files, if you need to find out the tempo of your songs, or if you need to find similar songs according to how they sound.
sauditor is a sample auditor that is intended to be simple and quick to use. It allows you to quickly and easily search for the sample you want. It features a curses interface, with no mousing required, and a toggleable X spectrum analyzer. The spectrum analyzer lets you see the frequencies present in your samples, which is handy if you want an idea of how much "space" the samples take up in the mix. It uses Jack for output, which allows you to connect filters to the output.
Scheme Note is a Scheme-like music file format and MIDI conversion tool. It takes a text file, which is a representation of a song, loosely tied to a MIDI-like event structure, and outputs a corresponding MIDI file. It is hand-editable for simple songs, and should be very easy to parse for a GUI.