The subject of midi files could probably spawn its own thread here, but for temporary continuity here are some thoughts...

There are three dimensions to the issue of copyright of a midi sequence... (1) The melody itself may be copyrighted (2) The arrangement may be copyrighted (even if the tune itself is public domain), and (3) The midi itself would be copyrighted, especially if the author has used his/her own arrangement to produce the midi.

I can't speak for other countries, but the Canadian Copyright Board has tackled the issue of music on the Internet by creating a new category... "communication of a musical work through telecommunication". In other words, they're treating midi neither as a "performance" nor as "publishing" in the traditonal hard copy sense. What they're really struggling with is determining what tariffs to put in place for such telecommunication.

Confusing? You bet!