You’re right — it’ll never happen — but it’s not for the reasons that you’re thinking of.

Creating charts in rhythm games isn’t something that could be automated. In games like Rock Band or Guitar Hero, the developers strive to (or at least, should strive to) make the charts “feel” similarly to how they would if you were to actually play them on a guitar. A computer program wouldn’t know the difference between a chord and a single note, nor would it be able to intelligently decide which of the five buttons would be a good match. You’d either wind up with uncomfortable, nonsensical patterns, or boring, repetitious patterns. That’s also assuming that the game would be able to tell the difference between a bass guitar, rhythm/lead guitar, drums, and vocals in the first place.

Finally, it’s also ignoring another serious problem: BPM calculation. Most of the songs in the Rock Band and Guitar Hero games have human drummers and, thus, use the movements of a human as a sort of “metronome.” If you were to sit down and work out the beats per minute of every segment of the song, you’d wind up with different values on just about every single beat. I imagine simply dealing with this would be half of the job of writing a chart, not to mention the reason why the timing windows of these games are so loose and why they don’t score based on hit accuracy.

This concept has been tried before with a Dance Dance Revolution style game. A company — I believe it was Codemasters — released Dance Factory to…well, dead silence. It had a problem with detecting BPMs. From personal experience, it sometimes failed to properly work out a usable BPM on electronic music with a loud bass kick and didn’t bother with BPM changes at all. The charts were also bland, lifeless, and didn’t have the same flow that you’d get on a choreographed dance game. Even Dancing Monkeys, possibly the best step chart generator for DDR-inspired games, spits out charts that are pretty sterile.

Oh, I forgot to mention the issue with time signatures above. Not every song is 4/4. Rock Band has several tracks by Dream Theater, for instance, and they are widely known for going way overboard with time signature changes. If the time signatures aren’t set up, the measure markers in the game won’t work properly.

If you can’t generate a convincing chart on the simplest of game types, there’s no way you’d be able to manage something like that for a band simulation game.

You might argue that they should allow users the option to create their own charts. That brings on a ton of other complications. Even getting past the fact that user created charts can never be as complete as a real chart without hacking (since getting a proper song with separate channels for the different instruments generally wouldn’t be doable for most, nor would it be a practical to support on a console), you still have to consider many other issues, most notably people being able to deal with the complexities of actually creating a chart.

For one, we have the aforementioned BPM issue. Many people who are new to creating DDR charts have this issue and, as I explained, there’s only so much that an automated program can do. It takes time and patience to be able to work this out. The person charting the song would also have to know enough about music to be able to work out the time signature that’s being used. You could argue that they could assume it’s all going to be 4/4, but that would make charting songs with different time signatures disorienting. The person creating the chart would also have to consider the offset of the first beat in the song and would have to place that accurately to avoid having the file start off-sync.

Secondly, the person who writes the chart would have to have a damn good ear. Harmonix and whoever-makes-Guitar-Hero-now have the benefit of being able to listen to each audio track individually. After songs are mixed, telling what part is what can range from being somewhat easy to being nigh impossible.

Finally, there’s the issue of distribution. Since, in most cases, the person who finishes the chart will not have rights to distribute the track, the only thing that would be distributable would be the data making up the chart. You could argue that it means that anyone who owns the actual song would be able to download and play it, but in practice you wind up with another mess on your hands. For one, not all compression schemes and audio extraction software is created equally. Worse yet, not all CD releases are the same. Some of them are remastered, some of them are rerecorded, and others are just flat-out different (i.e. removing a bonus track for a greatest hits compilation, etc).

The way I see it, even if all of the technical issues were resolved and this actually did happen, I can picture the end result looking sort of like what wound up happening with StepMania (a DDR simulator), and even things like Little Big Planet — too much user-created content available with absolutely zero quality control.

The Rock Band Network addresses many of the issues that I pointed out by putting the power into the hands of the bands. They can put together chart bundles that can theoretically match what Harmonix has in place and that can take advantage of all features of the game. It does some limited automation (which is probably reasonably accurate, since it actually has access to the individual audio tracks of the song, most notably the drum track) to lay down a bit of ground work for the file and to save some time for the author, then lets the chart author go crazy.

To make a long story short, I think that the way that Harmonix is approaching the issue is the most practical. Automatic generation simply sucks too much and putting it in the hands of the general populous would lead to far too many technical, quality, and legal issues.

Also, sorry about the wall of text. :]