Musical sequence
franktaw at netscape.net
franktaw at netscape.net
Wed Jan 18 20:01:47 CET 2006
It's not just those values. You want all ratios up to a certain "size" to be approximated well - increasing this size is more important that getting a better approximation. There is no obvious definition for size. In general, divisibility only by small primes is important; 9/8 is clearly superior to 7/6, for example.
31 works pretty well.
Franklin T. Adams-Watters
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-----Original Message-----
From: Jud McCranie <j.mccranie at adelphia.net>
To: David Wilson <davidwwilson at comcast.net>
Cc: Sequence Fans <seqfan at ext.jussieu.fr>
Sent: Wed, 18 Jan 2006 13:46:40 -0500
Subject: Re: Musical sequence
At 01:40 PM 1/18/2006, David Wilson wrote:
>In general music theory, we hold to the concept of an octave, >specifically, that if a musical scale includes a tone of frequency f, it >also includes a tone of frequency 2f.
>
>What if we abandon the notion of octave, but keep the idea of equally >spaced tones, so that our scale can be described by base tone frequency b >and a ratio r between adjacent tones on the scale.
>
>Is there a measure of goodness of r that would rate r = 2^(1/12) high? >Presumably this rating would be based on the closeness of tone ratios to >simple rationals which represent pleasing harmonies. Given this rating, >what would be the best r? If we return to octave-based scales, could be >construct a sequence of t with increasingly better ratings of 2^(1/t), >which would represent increasingly good choices for number of tones in an >octave?
I looked at this sometime ago. The important thing about 12 equally-spaced tones is that r^4 is close to 5/4, r^5 is close to 4/3, and r^7 is close to 3/2, r is the 12-th root of 2, as above. The next values that come close to these important values are when there are 43 and 53 equally-spaced tones between frequencies f and 2f, IIRC.
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