I have to disagree with this. You could play music that sounds just as natural using a series of 6 or 8 perfect fifths. *Any* number of notes separated by fifths sounds natural.
12-tone equal temperament is useful because 2^(7/12) is close to 3/2. In 19-tet, 2^(5/19) is close to 6/5 (minor third), 2^(6/19) is close to 5/4 (major third), and 2^(11/19) is close to 3/2. That makes these exponential divisions of 2 useful for *fooling* the ear, but in all cases they are approximations, and 19-tet's substitute for 3/2 is farther from it than 12-tet's.
I say if you want 3/2, use 3/2.
I don't think 5-tone equal temperament is a substitute for the pentatonic scale. The pentatonic scale is made up of decidedly uneven intervals. Javanese gamelan tuning is notoriously non-standardized, adjusted individually for different ensembles. They usually don't even use octaves. http://www2.hmc.edu/~alves/laras.html
Also, it is not true that all intervals are based on fifths. Anceint Chinese theorists suggested this, but their anceint Chinese secret was that the Ch'in used intervals not derived this way, such as 8/7. Ptolemy and Didymos both suggested tuning thirds based on the 5th harmonic, 5/4, rather than Pythagoras' 81/64, which is more out of tune than 12-tone equal temperament. Islamic theorists used intervals like 18/17, 81/68, and 27/22, supposedly because it was simply easier to tell people where to put the frets that way. This part is more against the Jeans quote than the article, though.
BTW, he mentions the idea of 7 plus or minus 2. George Miller's essay on this idea is awesome: http://www.well.com/~smalin/miller.html One thing he mentions, that I think dispels the idea that the 7-tone scale is inviolable, is that folks can recall longer and longer series if they form a vocabulary of smaller parts, i.e., become more familiar with the material. How else could we differentiate 26 letters, or remember 10-digit phone numbers? Or recognize hundreds of people on sight? Cross-categorizing- Identifying a fat, bald man in a blue shirt is far easier than recognizing someone based on any one of those criteria. A melody is far easier to recognize than a single note.
-Chuckk