What is FMOD?
FMOD is an easy to use crossplatform audio engine, available on the Windows, Windows CE, Linux, Macintosh, GameCube, Playstation 2 and XBox platforms. It can be used with C/C++, Visual Basic,Delphi and MASM. So, if you use one of those languages on one of these platforms and you want to use sound in your application, FMOD is made for you. The examples below will be in C although thebasic principles should be the same across all platforms.
One alternative might be OpenAL. OpenAL is another crossplatform audio API which is available for Windows, Linux and Macintosh and can be used with C/C++,Delphi and Java. The style is similar to OpenGL (for example, the extensions technique is also used here).
A Windows-specific alternative would be DirectSound which is part of Microsoft's DirectX.
What does it cost?
The developers of FMOD have a nice philosophy; if you don't intend to make any money with your project, you can use it for free. So as long as you don't make any profit with your program you don'thave to pay anything. However if turns out that you will sell your product you would then have to buy a license, starting at $100 for shareware products. For more details have a look the officiallicence price list at fmod.org.
From where can I get it?
To use FMOD in your application you need the headers and the library which can be downloaded from http://www.fmod.org. At this time the recent version is 3.70. Beaware that this version is not backwards compatible any more!