hexter is a software synthesizer that models the sound generation of a Yamaha DX7 synthesizer. It can easily load most DX7 patch bank files, edit those patches via a built-in editor or MIDI sys-ex messages, and recreate the sound of the DX7 with greater accuracy than any previous open source emulation (that the author is aware of). It operates as a plugin for the DSSI Soft Synth Interface.
METAXPON ("Metachron" in Greek letters) is a small and fast audio DSP library for time-scale manipulation of 16-bit integer or 32-bit floating point stereo audio data streams. It employs a rigid phase-locked vocoder with dedicated transient detection and processing, and can work in real-time or non-real-time. Four editions are included - a portable edition and three x86 editions. The portable edition can be built with any ANSI C compiler and is OS- and architecture-independent. The three x86 editions are written in assembly using the FPU, 3DNow!, and SSE instruction sets, respectively, with automatic selection between them depending on the CPU capabilities. They can be compiled with MASM, JWASM, or NASM, producing libraries of object files in 8 formats.
DeaDBeeF is an audio player for GNU/Linux and other UNIX-like systems. It is written in C with some plugins in C++. It has minimal dependencies, a native GTK2 GUI, cuesheet support, support for MP3, Ogg, FLAC, and APE, chiptune formats with subtunes, song-length databases, and more. It is very fast and lightweight, and extensible using plugins (DSP, GUI, output, input, etc.). The GUI looks similar to Foobar2000.