Hi... here's a page that gives instructions on embedding midi files...

http://www.faeriekeeper.net/midi.htm

Note that there is a volume control (unlike other sound sources) so it's probably just the instructions that your midi player is getting to start off at a low volume... Also note that they instruct writers to do it that way so as not to cause the music to suddenly start blaring. (something I can certainly appreciate )

If you're curious as to the settings you can click view>source to see what the volume control is set at and compare it to other pages with midi files...

(It opens in notepad so it may save time if there's lots of code to do a search -edit/find- for the word "volume")