MP3s are very high quality, encoded to using the LAME codec (program), widely acknowledged as the best MP3 encoder available.
All files added SINCE JANUARY 2006 are encoded at the maximum possible quality of 320 Kbps Bitrate. Some files added to our systems PRIOR TO JANUARY 2006 are encoded using Variable BitRate (VBR) encoding. This means that the bitrate changes during the file, saving space where the maximum encoding level is not required. We have been working to upgrade the whole catalogue and have completed nearly all of them now. If you receive a file that is less than 320kbps and are not happy, we will upgrade it for you.