Is there any technically feasible way to create some kind of 'standard' volume? Alternately, what about client side solutions?
A client side solution is certainly possible, but as you'll see from the 'loudness war' the enemy is not so much peak audio levels as dynamic compression, which means a piece of music can end up seeming too quiet and too loud at the same time. Awesome. You can't really code this away because it would essentially require de-mixing (a hard problem) and then re-mixing with good taste (something that's frequently lacking even in wetware).
One way to come closer to a standard volume would be to establish a 'law' that says "no recording should be louder as x DB RMS). Every recording could be squeezed into such a dynamic, for example, by deploying compressors.
But there are two problems. 1) Different recordings need different frequency ranges. If you would compress classical music as hard as pop music is compressed, chances are the listening experience would be completely ruined. 2.) It's not just volume that influences how loud something is perceived. Material which has emphasis on 2khz would be perceived much louder than something that is just as loud but around 80 hz. (See Fletcher-Muson Curve[1])
However, there is a non-profit organization that somewhat tries to solve your problem. They don't aim for "standard volume". But they try to bring back dynamic into audio recordings.(Today most stuff has a very small dynamic range)
Read this: http://www.dynamicrange.de/en/our-aim
I hope I could help a little. Sorry for my poor English.
[1]http://en.wikipedia.org/wiki/Fletcher%E2%80%93Munson_curves
edit: Where are the guys from Ableton? Perhaps they could enlighten us :-)
This is because only the loudest signal hits 0db then. If a signal is on average mainly quiet, it will stay quiet. And if it is pretty loud, it will stay loud.