mp3PRO Audio File Format
The MP3PRO file format was developed by Coding Technologies to provide enhanced compression to the MP3 system. Files can be up to half as small using MP3PRO.
MP3PRO was designed after MP3s had been in use for a while, and many users had sacrificed the high quality sound in order to create smaller files for use in internet radios and on portable devices. Coding Technologies felt there must be a way to make these smaller-sized files sound better. The system they used to do this is SBR, or Spectral Bandwidth Replication. It specifically helps increase the audio quality of those small-bit files.
The MP3PRO therefore doesn't help much with the higher quality and larger sized files. While there are improvements with the lower quality files, it is not a stunning difference. Also, since most players and software packages do not support MP3PRO, using this as a file storage system might ensure that your songs are unplayable on most players you could want to buy.
Music Format Types
Music / MP3 Tips and Information