"assumes that no two CDs will contain the same number of tracks with matching lengths in the same order. Obviously it is possible, as in the case of the two Scottish CDs, for two CDs to have matching track lengths and therefore give an incorrect identification"

It's just like hash tables in computing - more than one input can give the same hash code, and there is only only space in a hash code table to have one item, so you have to have a way to record and identify other inputs that match the same hash code.

Obviously Gracenotes was designed by someone who had did not understand 'the appropriate field of research'... :-)

Theory DOES have its uses.... :-P