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

Software tuner for linux.

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.

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.

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.