Categorising music albums

I've had heaps of albums on my PC for a few years now, but since I got the iRiver, access to albums had to be made faster. Without an iPooed wheel that quickly scans down lists, I devised a makeshift folder system to divide up the files, figuring that I could classify my albums into about six categories. While it's worked well, the sheer volume and variety of albums has crowded up the lists and now it's not so organised after all. Including podcasts, standalone tracks and a few other files, my iRiver is currently hosting 644 folders with 5851 songs.

On the original pH-style "PH" scale (named after yours truly), the genres are:

• 1 Light
• 2 Pop Rock
• 3 Rock & Roll
• 4 Rock
• 5 Heavy Rock
• 6 Metal

Light is softer rock, with more ambient/creative stuff such as Evermore, Travis or Pete Murray. Critics could say the "You know how I know you're gay? You listen to Coldplay/insert band from Light" a la The 40 Year Old Virgin principle could also be in place here.
Pop Rock is Indie like The Killers or Franz Ferdinand and Australian quirky but rockin bands like Eskimo Joe or Little Birdy.
Rock & Roll is traditional guitar-solo-ripping 60s/70s influenced stuff like Oasis, Wolfmother or Jet or even 50s/blues influenced stuff like The Hives or The White Stripes.
Rock is the umbrella term for rocking guitar/bass/drums stuff like Foo Fighters, Red Hot Chili Peppers or Smashing Pumpkins.
Heavy Rock has more metal/nu-metal edges, stuff they play at Switch like Papa Roach, Linkin Park or Evanescence.
Metal is another umbrella term, spanning System of a Down, Nightwish, Sevendust, Metallica, Dream Theater and beyond.

It's awesome because if you recognise, say, three bands in one folder that you like, the others are probably going to hit a few right notes for you too. Depending on the broadness of your taste, you'll probably enjoy albums either side of your favourite genre too. When I don't know what to listen to, I can also work out what mood I'm in from 1 to 6 to narrow down what I'm going to put on.

I had to add "Comedy", "Punk", "Soundtracks" and "Other". "Soundtracks" in theory could be split up, but I'd need a Pop or Novelty folder for that (which I'll probably do). The "Other" folder started because I can't classify Radiohead (suggestions welcome!), then continued because I felt Jamiroquai and Massive Attack were too electrish and has now become the "To Be Sorted" folder as well. Pop Rock also became so big I chucked it into A-K and L-Z phonebook-style. The realistic divide there is Indie and Aussie Pop Rock bands (for some reason Indie's all overseas bands, must be a cultural thing). Metal needs a fair bit o' work too, like a nu-metal folder for one, but thankfully there's no shortage of friends willing to discuss the finer genres of metal!

Ideally, all genre folders should have no more than 16 artists inside, because the iRiver display shows 8 at a time (and I can scan from top or bottom). That's a bit of extra categorising, but not impossible. Secondly, it's gotta continue making it logical for people to know which of my music they should thieve.

Another problem is how to insert dance/techno/electro/whatever music in there. I'll probably expand the left (Light) edge to pop then dance, then techno...but anything without traditional band instruments is really tough for me to classify, even in a consistent way to myself! At least I can deal with more punk/heavy rock distinction.

Clearly it's still very early stages, but having typed it out it seems a bit closer to reality. I've still got a few dozen albums I'd like to go through and see if there are categories I'm not thinking of first, but by the end it should be an easy way to recommend albums to people by gauging their preferred genres to start with and expanding outwards. From there, I wouldn't mind creating/using a database for the Internet at large to check albums in the collection (not just ones I've bought) along with the genre, date it was added and the source (i.e. recommender) and stuff like that. Can any readers out there recommend something like that?

Has anyone out there seen or devised their own genre classifying organisation system? Particularly ones using similar sliding scales or multi-dimensional plots (like the Political Compass)? Does anyone have a program to help list out my current albums based on directory structure too?