Sync XML playlist with Next Button of sliding panels widget.

Ah, so the desired behaviour is you want to be able to control the flash widget (ie., to play a certain song) when the "next" HTML link is clicked, from Javascript.

This is unfortunate as the current set-up looks to be working pretty well as-is. Using SM2 would get you better control from Javascript, but you would pretty much have to re-write the rest of the player UI to get what you currently have with the Flash stuff. :/

What I might look at doing instead is when "next" is clicked, re-loading the Flash widget with a different playlist file that has the desired song first in the list, and then it will play from that point.

It might be a little tricky, but you can re-write content to a DIV generally with innerHTML (or in this case, a SWF using SWFObject or whatever JS library you might have) - and if you can specify a parameter to a playlist file, then you can have different playlist files for different "first songs".

This discussion is outside of SoundManager 2, so I might look at the forum/support for the flash widget you're using to do the MP3 playing currently.

Best of luck!