I'm silent in Firefox!

I'm using Yahoo Sitebuilder to build my web page and it's set up to play background sounds in Internet Explorer only, in spite of what it's help section tells me. I can hear the background sound I put on the page (it's not an annoying loop, just a one-time welcome!) and I can hear it if I use Internet Explorer to go to my page, but not if I go to my page in Firefox.
I have tried to put html code into the section that's in Sitebuilder, adding "embed src="mysound.midi" hidden="true" autostart="true", but that doesn't work. If I put the complete address of my sound on my own computer, starting with C:, it still doesn't work. I need to find a way to make this sound play for every visitor to my page. I know Sitebuilder is very rudimentary, but I had to throw something up fast, as the name of my site is up for review as a "service mark" (like a Trademark) and the powers-that-be will be dropping into my website any minute to check if I'm really doing business under that name.
I sure hope you experts can give me an idea about this...I despair of reaching the support at Yahoo, which is well buried and usually gives a canned answer that's totally off-topic. Thanks! Shoshana