Mike: Here's the scoop. The BIG plus about Yamaha created midi songs (.mid) are that they are automatically GM midi compatible so will readily play on your computer soundcard or thru an external GM sound module or keyboard without any file conversion needed. The limitation is that the sound quality you get thru a GM sound module is only as good as the sound quality of the GM soundcard/device/keyboard you're playing it thru.

When this same file (.mid) is played on the Tyros itself, it maps the sounds to the Tyros specific (non-GM) instruments that were originally intended. For example, the song you mention includes the new exeptional mega (guitar) voices of Tyros.

The MP3 version sounds better because you're hearing the new Guitar mega voices and not just your computer's GM guitar soundcard. Still, because the MP3 format is a highly compressed, it important to remember that the song will sound even MUCH better when heard in CD Quality uncompressed WAV file format or directly LIVE thru the Tyros itself.

Hope that helped answer your questions.

Scott