Researchers at the Max Planck Institute for Biological Cybernetics in Tübingen have published a paper (PLoS Biology, June 20, 2006) on the results of their fMRI study into mapping where the human brain processes tones and tone combinations. ScienceDaily has a good write-up on the paper for those with a basic technical understanding of how the auditory system works.
The study seems to have produced a more detailed understanding of the mapping between the cochlea and the Auditory Cortex Fields (ACF) of the brain, where the processing (is it separation and/or decoding?) of tones takes place, as well as the organization of the ACFs.
(Hat tip: ScienceDaily)