hi,
The field of audio Editing is one of the most important topics in media production.
For Linux, There are many applications that can do the job professionally
and even much much better than Windows OSs.
One of them is Audacity, which is a greate sound editor,
Here you can do anything you like, starting from simple editing for a sound file
to changing speed, pich, echo,......, filtering even at the sample level.

Also, there is Glame, another greate and full featured digital Audio Editor.

I have used the both all the way, and they are working greate under FC4.

khaled