I think there's a tendency to not use music during the introduction to a site, because it may surprise the user and be a problem if they're surfing at work.

I also think there was a stigma attached to the use of MIDI files a few years ago, partly because of the unpredictable sound quality based on the user's sound card.

When do you think it's appropriate to have music playing when someone goes to a site?

It's fine for me to have music background in the site as long as you can turn it on and off. It would be great if there are many songs available because we are not of the same taste of music. If I love listening mellow songs and you'll play hip hop, it will surely irritates me.

I don't think it's appropriate at any time. Let's say I have music playing already from my favourite music player and I visit a website that's playing music in the background. It's annoying to hear 2 songs at the same time, even if I can turn it off on the website.

Movie sites alone, having music in the background is no longer a good idea for websites. Honestly, if your site is so boring it needs a soundtrack, music is the least of your worries.

I agree with Lukero and Sneakyheathen. I don't think websites should ever have a musical introduction.