CSCore
An advanced audio library, written in C#. Provides tons of features
...CSCore is a free .NET audio library which is completely written in C#. Although it is still a rather young project, it offers tons of features like playing or capturing audio, en- or decoding many different codecs, effects and much more! CSCore is based on a very extensible architecture that allows you to make it fit to your needs without any major effort. You can build music players, voice chats, audio recorders and so on! Supported platforms, Windows only, Linux and mac experimental. Optimized performance though the usage of CLI instructions provided by a custom post compiler.