If it works on my pages but not yours it could be the way the DT server is set up. There's a page here that discusses the mime types that need to be set up on the server.

I've found lots of pages with suggestions - the trouble is none of them worked!!

Let's see - good news - isn't there a song that goes, "The Sun Will Come out Tomorrow..." That's the extent of my optimism when it comes to troubleshooting midi problems any more! I used to be pretty good at it - another skill passing into obsolescence...