As said in the forum, a SoundManager class has been created (and some other stuff, around, too), internally using OpenAL - a free audio library designed for video games. It is now possible to play musics and sound effects.
Are currently supported only .wav and .ogg files (but, anyway, mp3 is bad).

Sound definitions are stored in .sound files (in xml), but it is also possible to define them on the fly directly in C++.