Audacity does let you edit the file, though it takes a bit of playing to understand the steps. An easier application is the desktop companion to RingCare; check it out at
www.gotreosoftware.com.
If I have bunches of files to do (not too often), I use Audacity to make them and then Switch to convert them en masse. If I have only 1 or 2 to do, then I use RingCare Desktop.
Ben