Imtelephone
- Provide Win32 static linked codec libraries with source code implementing ITU G.722, G.723.1, G.729a, G.726, and G.728. Also provide audio arithmetic such as AEC, VAD, AGC, VoiceXML. [Commercial]
- http://www.imtelephone.com/

Ethan Brodsky's Sound Programming Libraries
- Sound libraries for the PC-DOS platform.
- http://homepages.cae.wisc.edu/~brodskye//

OpenAL
- A free (LGPL-ed) and open source, cross platform audio library used for 3D and 2D sound.
- http://www.openal.org/

DMM_Volume_DLL
- The control of volume is realized by the u32 library. The library can work in all the MS Windows versions (95, 98, ME, NT, 2000 and XP). [Commercial]
- http://www.dmm.cz/en/dmm_volume_dll.htm

Spark
- A sound engine for Windows. It provides powerful sample, streaming, and module playback functions and can be used with and without DirectSound. It distributed in two forms: static (.lib) or dynamic (.dll) libraries.
- http://web.axelero.hu/egzo/spark/

Digital Room Correction
- DRC generates digital room correction FIR filters to be used within HiFi systems in conjunction with real time convolution engines like BruteFIR. [Aladdin Free Public License (AFPL)]
- http://freshmeat.net/projects/drc/?topic_id=114

GSI (General Sound Interface)
- An audio system with network support and provides the ability to use stereo, 3D audio, doppler effects, music playing (MIDI, HMP, MUS), and cd playing and ejecting/changing. [Open source, BSD License]
- http://gsi.sourceforge.net/

DUMB - Dedicated Universal Music Bastardisation
- A high-quality IT/XM/S3M player library. Versions 0.9+ will have MOD support. An add-on is available for playing OGG files. [Freeware]
- http://dumb.sourceforge.net/

Virtual Sampler SDK
- Provides applications running on Pentium-class PCs under MS Windows 9x/NT/2000 with a MIDI-controlled, low-latency, fully programmable wavetable module implemented entirely in software. [Commercial]
- http://www.polyhedric.com/software/vssdk/

ALSA (Advanced Linux Sound Architecture)
- An audio library (and kernel level API) for Linux.
- http://www.alsa-project.org/

BruteFIR
- A software for applying long FIR filters to multi-channel digital audio, either offline or in realtime.
- http://www.ludd.luth.se/~torger/brutefir.html

FMOD
- A sound system on Windows, Linux and Windows CE, PS2 and XBox.
- http://www.fmod.org/