Here's a demo page showing how to auto-start a background tune with visible controls. This is done using the following REFRESH code in the HEAD section of HTML:

META HTTP-EQUIV="REFRESH" CONTENT="15; URL=yoho.mid"

This control does not always work due to timing problems with page loading. Most (possibly all) browsers will not do the redirect if they are busy when the specified time arrives, e.g. loading images, so the delay time needs to be set high enough to ensure that the page has had enough time to load completely. This may require some experimentation, preferably over a slow 14.4K modem, which is what your user may be stuck with.

The "15" shown here is a 15-second lag before launching the default MIDI player. You may need to play around with this parameter based on the relative file sizes of your main page and sound files to get best results. This page has no graphics, so we could use a pretty short delay. (Your mileage may vary.)

Notice if you leave this page, the music does not stop playing. That's because it's being controlled by a separate floating control. For a clever background music effect that will persist across an entire site, launch the musical theme from the home page and let it persist in the background while your visitor tours. Looping is often a BAD idea, but in this case it might be useful.If they don't like the music they can turn it off easily.