windows command-line program to change the volume of an mp3 file

I can use audacity to increase the volume of an MP3 file. However, if I want to use this on a regular basis it's a hassle, since I have to fire up audacity, load the file, increase the volume and finally export it back to MP3.

Is there any command-line program I can use that will increase the volume?

Answer

mp3gain can do this:

http://mp3gain.sourceforge.net/