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.
The CMU Midi Toolkit (CMT) is a collection of software for writing interactive MIDI software in C. It includes a number of handy utilities along with an application "shell" that provides timing, scheduling, and MIDI interfaces that are portable across DOS, Mac, SGI, and Amiga platforms.
libmls is a library that can be used to measure the frequency response of a loudspeaker or a room using your computer and an ordinary soundcard. It can perform both MLS (Maximum Length Sequence) and Sinus sweep measurements. It supports ALSA, OSS, and the sound system used in Windows.
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.