How do I advance a pp slide at a specific point in a music file after starting the music file?

[WPCentral Question]

I am using powerpoint to display childrens songs. I want to bring up a slide, explain the actions etc then click the music file to start the song playing. I want to set the timing so that the slide advances at a specific time in the song, ie the timing begins from the point I click the music file icon onscreen (and not from when the slide first displays). I can't use 'delay' as my explanation will change in length depending on when I am presenting. The slide advancement needs to be linked to the timing in the song. How do I do this? (I know how to time and automatically advance slides for following verses. My problem is when its the first verse and I need to talk prior to the song starting.)