From Kevin Schneider:
MP3 Quality Modifier is a straightforward program that is able to easily change the quality of your MP3's in order to save disk space and/or to fit more music on your MP3 player while maintaining the desired level of audio quality and keeping all ID3 tags intact.
The program is pretty simple to use: The first step is to drag and drop MP3 files on the file list. Various information such as the name, interpret, size and bit rate are displayed automatically.
The next step is to select a preset which ranges from high quality over portable and compromise to low quality. More advanced users can choose from a variety of configurations such as bit rate mode and rate, sample frequency and the stereo modus.
The process itself takes only a few seconds per song and is even able to adapt the folder structure (example: "Artist X" folder with "Album 1" and "Album 2" as subfolders) if that is wanted. Unlike other tools all ID3 tags like the title, artist etc. are automatically retained as well.
Finally the result window allows comparing the original and created music files by listing their size differences.
What's new in this version:
Version 2.2 added support for MP1 and MP2 files, new "Best quality" preset, and fixed small error during calculation of bit rate.