nest @ The Echo Nest is a blog by the Echo Nest guys. There's a post mentioning artist identification results for 2005. With numbers showing that a system named "Cepco" outperforms MFCCs.
I asked Google (maybe I didn't ask correctly) but Google doesn't seem to be aware of any publications mentioning a Cepco system (sounds like CEPstral COefficients, doesn't it?). In 2005 Mandel & Ellis submitted a nice approach to artist identification using MFCCs and SVMs. I'm guessing that at about the same time the Echo Nest found a similar or maybe nicer solution to artist ID?
They also have a post on the world of music criticism. The numbers could be anything (e.g. term frequencies?) but I guess it does mean that Brian and his team have continued research on automatic record reviews?
My favorite is this interesting post. What's so different in the two figures? Anyone have a guess? :-)
If it's a visualization of features extracted from audio then here are some guesses I'd make: Maybe everything (input, algorithms) was the same for both but one of the audio signals was slightly shifted in time? Or maybe they used some rescaling (e.g. loudness compression) techniques on one of them and not on the other? Or maybe one is a cover version of the other?