Why buy? Do a google or yahoo search for "midi files" or "title of song midi". I also use these two sites; all for free
You will find that most midi files are voiced for GM (general midi), GS (Roland) or XG (Yamaha). Yout Tyros should be able to handle any of those. The only way to get truly Tyros midi is to edit a file with instruments of your own choosing.
www.musicrobot.com www.vanbasco.com ------------------
www.cassponline.com/