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Eugine_Nier comments on Harry Potter and the Methods of Rationality discussion thread, part 15, chapter 84 - Less Wrong Discussion

3 Post author: FAWS 11 April 2012 03:39AM

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Comment author: Eugine_Nier 13 April 2012 06:23:41AM 3 points [-]

Notes sound good if they're approximately simple rational multiples of each other. Hence you want your scale to contain multiples.

Since the simplest multiple is x2 we use that for the octave. As for why we break it up into 12 semitones, the reason is that 2^(7/12) is approximately 3/2 and as a bonus 2^(4/2) is a passable approximation to 5/4.

Comment author: Alsadius 13 April 2012 03:06:35PM 0 points [-]

I'm referring to the name. What relation does it have to eight?

Comment author: Random832 13 April 2012 03:24:33PM *  3 points [-]

Eight notes: C D E F G A B C. (People used to not know how to count properly.* I think it comes from not having a clear concept of zero.)

* One can argue that this counting system is no worse than ours, but to do so, one would have to explain why ten octaves is seventy[one] notes.

Comment author: gjm 13 April 2012 10:35:02PM 2 points [-]

Similarly, other musical intervals -- i.e., ratios between frequencies -- have names that are all arguably off by one. A "perfect fifth" is, e.g., from C to G. C,D,E,F,G: five notes. So a fifth plus a fifth is (not a tenth but) a ninth.