RE:

Jim Savage wrote:

>>>I presume you use a 7/4 ratio for the G7 minor7th because it's the 7th
>>>harmonic of G, no?
>
>>Yes. Anything else would be out of tune.

>Sorry, I should have elaborated. Pardon my ignorance, but I don't
>understand, unless it's voice leading considerations (?), but the minor 7th
>in the Dmin7 chord is in tune at 9/5. There'st more stuff on the web I
>should read before asking more inane questions in this direction, but all
>suggestions of good reading on why certain ratios are best in one chord and
>not another would be most welcome.

It's pretty simple in this case. In a Dmin7 chord, you've got a Dmin,
presumably 1/1 6/5 3/2. Where should the seventh be? Well, 9/5 forms a 3:2
consonance with 6/5 and a 6:5 consonance with the 3/2. Any other seventh
would fail to be as consonant. In a dominant seventh chord, you've got a
major triad, 1/1 5/4 3/2. A 7/4 forms very simple ratios with all other
chord tones: 7:4, 7:5, and 7:6. No other seventh would be as consonant
there.