Well Willem,

It all depends on what you are looking for. I find using the advanced mode of Google the most beneficial. Enter the style of MIDI file you are looking for and add the one word that must appear “free”. Then select the country. While I suggested Japan, I’ve found excellent files in Italy, France, Russia and a number Spanish speaking countries.

Here is a well played site with original compositions mainly for the piano in Japan:
http://www.geocities.co.jp/Broadway/5854/midistaj.html

And, here is a good jazz site in the U.S.:
http://www.alisdair.com/jazzpages/jazzmidilinks.html

Happy hunting,
Frank