>> I beleive the average human has difficulty distinguishing between tones 10-20 cents apart in the vicinity of middle- c, it may be different in other ranges, I am not familiar with the literature on this, just one of the odd factoids I recall from a life of interest in technical trivia. I do know it matches up with my personal experience; well, some of the time anyway.
++Psychoacoustics experiments on human subjects have demonstrated that pitch discrimination is most sensitive in the frequency band that occurs in the middle of the range of human hearing (including middle C). The resolution falls off considerably at both ends of the range. Humans find it much more difficult to discriminate pitches that are very low or very high frequency. To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
