Do you mean that the browser would open it in something like quicktime, instead of opening the "save file" dialogue?
If so, hmm... That's actually a per-browser setting for the default behavior of clicking on an mp3 link--you can have your browser configured to save an mp3 when you click on it, instead of opening it. But most people don't have it that way, or don't know how. So I understand the need for a fix.
Is there no other way? Something like a parameter in the href tag?
I'm wondering if removing the redirection would allow links-with-spaces, too, instead of %20's.