Paul S. Sorry it's taken me a couple of days to get back to you. Had to ask my brother about this. He did some research into the permutation thing a few years ago and found that Leonard Bernstein was also interested in such things. Had a mathematician friend of his work up the numbers. While using the twelve tones, one melody line only, no harmony, reached a number of almost infinity, by adding a second or harmonising line, it went beyond infinity to something the mathematicians call aleph nul. So, while your "large number" may be right, as close to infinity as can be; there can be endless permutations which include harmony. He didn't have his reference books handy, but if you want more info and can't find it on the nect, I will get it from him, soon.

kat