For one project I needed to play midi files on the page. Of course this should work on most browsers (IE6, well I don't take into account). But, as I understand it, either you need the QuickTime plugin, which is not on every machine, or Flash, which judging from what you've told me Google, midi is not able to work, or the audio tag, which is not everywhere implemented in FF, for example, midi is also not friendly.
In General, I'm surprised. The old format used (in the circles of musicians), and support tight. Does anyone have the options to stick a midi playing on the page?