Here's a screen of my progress with Extjs, planning on having an accordion that separates the middle area. Sort of like a toggle between file browsing and the playlist.
What about releasing the code open-source ? If you agree with that, it would be cool to make up a git repository with the latest source so we can all help you making this better

If you dont know how to install a git repo that can be used by others, just go to github, they have a free and easy sytem for open-source. And if you happen to not like the company behing github, I offer my services : i have a git repo waiting for you, or some time to help you put up a new repo by yourself !
And if you fear that git is going to make it painfull to continue coding since you'll have to merge files from other developers, let me tell you : git meges by itself, no more problems, it's realy realy easy and powerfull !
Will this frontend support a tree view that is capable of drilling down multiple levels, so that any album can be reached no matter how many folders it is buried in?
I'm also hugely interested in such a feature (having lots of problem to sort out my entire library

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But for what I've seen, it's not included yet, and since there is little use of the databes, it's not coming soon since we'd had to "merge" all songs by analysing the tags and keep a record of this "merge".
But this might come very soon if the source is released in it's latest stage (No point in working separately, but I was willing to start a php project to do just that

)