http://www.ambiera.com/irrklang/features.html

irrKlang Features
irrKlang is a powerful high level API for playing back sound in 3D and 2D applications like games, scientific visualizations and multimedia applications. It is a cross platform 2D and 3D sound engine and audio library, usable in C++ and all .NET languages (C#, VisualBasic.NET, etc) and provides useful features like lots of built-in file format decoders (wav, ogg, mp3, mod, xm, it, s3m...), a sophisticated streaming engine, extendable audio reading, single and multithreading modes, 3d audio emulation for low end hardware, a plugin system, multiple rolloff models and more. All this can be accessed via an extremely simple API.

irrKlang is free for non commercial use. There is also an advanced version of irrKlang named 'irrKlang pro' which can be purchased for a small license fee and may be used in commercial products.

Feature Overview
irrKlang's current features are:

Plays multiple file formats, .WAV, .MP3, .OGG, .MOD, .XM, .IT, .S3M...
Buffered and streamed audio playback, in 2D and 3D.
irrKlang is platform independent: irrKlang runs on several operating systems including Windows 95, 98, NT, 2000, XP, Vista, Linux, Mac OS X (Intel as well as Power PC).
High level resource management and autodetection: The engine can do everything for you. Just tell it to play a sound file, and it will load, cache and/or stream sound data for you automaticly, depending on what is best for performance and memory usage. But if you want to specify how the engine should handle this, you can do this as well.
Sophisticated 3D sound engine designed to be used in games.
Extendable: Possibility to write own file format readers/decoders to extend the engine with it.
Sound effects such as the doppler effect for 3D sounds or 2D effects like echo, reverb, distortion, flanger and more.
Exact seeking and position retrieval in streams and buffered sounds.
Plugin System: Simply copy external created plugins to the place where irrKlang is being used and extend its functionality with it.
Works with multiple compilers including Microsofts VisualStudio 6.0™, VisualStudio.NET 7.0 - 8.0™, and with g++3.2 - 4.0, also with support for Code::Blocks and XCode.
Multi/Singlethreaded modes: The engine can run both multithreaded or singlethreaded in the same thread as your application, to make it possible to debug your application easier for example.
Low level audio output manipulation: Possibility to alter any aspect of a playing sound like panning, volume and 3d position.
Sound event call backs.
File reading functionality can be overwritten by the user, of course, making it possible to let irrKlang read from own file archives for example.

Supported File Formats
irrKlang currently plays back the following file formats:

RIFF WAVE (*.wav)
Ogg Vorbis (*.ogg)
MPEG-1 Audio Layer 3 (*.mp3)[2]
Amiga Modules (*.mod)
Impulse Tracker (*.it)
Scream Tracker 3 (*.s3d)
Fast Tracker 2 (*.xm)
In addition, it is easily possible to extend the playable file formats using plugins. If you need irrKlang to playback a file format it doesn't support yet, just contact us and we can add it for you.

[2]: MP3 playback is done via a plugin which comes along with irrKlang (and its full source code) so that it is easily possible to remove mp3 support if wished. If you are using mp3 playback in your application, you might need to purchase an mp3 license from Thompson Multimedia as most software using mp3s has to, although there are special prices and conditions for games.

Supported Platforms
irrKlang is cross platform and works for the programmer the same, independent of the platform it is running on. The following platforms are currently supported together with the corresponding sound output backends:

Windows 98, ME, NT 4, 2000, XP, Vista
DirectSound 3
DirectSound 8
WinMM
Linux / *nix
ALSA
Mac OS X (x86 as well as PPC[3])
CoreAudio
The sound library works with all supported platforms the in the same way, the programmer only has to write his game/application code once, and it will run on all supported platforms without the need of changing one single line of code.

[3]: Currently, the PowerPC version does not support module file (.mod, .it, .s3m, .xm) playback. All other features are supported.