QEMU is a generic and open source processor emulator which achieves a good emulation speed by using dynamic translation.

Wired supports unlimited Audio/Midi tracks playback and recording, and introduces a Plugin system for instruments and effects.

Hydrogen is an advanced drum machine for GNU/Linux. It's main goal is to bring professional yet simple and intuitive pattern-based drum programming.

MusE is a MIDI/Audio sequencer with recording and editing capabilities written by Werner Schweer. MusE aims to be a complete multitrack virtual studio for Linux.

Freecycle is a beat slicer running on GNU/Linux platform using the QT toolkit, providing amplitude domain and frequency domain beat matching / zero crossing algorithms.

Software tuner for linux.

Ardour is a digital audio workstation. You can use it to record, edit and mix multi-track audio. Produce your own CD's. Mix video soundtracks. Experiment with new ideas about music and sound. Generate sound installations for 12 speaker gallery shows.

Cool app to analyze log files with.