Re: [Harp-L] Why use the term "perfect" to describe a perfect fourth or a perfect fifth?

[Dave Land <land@xxxxxxx>]

Folks,

As I understand it, the so-called "perfect" intervals (recognized for their consonance long before anything like music theory came along) are considered "perfect" because they are so strongly consonant. This is because the ratio of the frequencies of the two notes in the interval may be expressed in small integers, resulting in very low harmonics.

    Unison: 1:1
    Octave: 1:2
     Fifth: 2:3
    Fourth: 3:4

As music developed (and music theory was created to explain it), more "complex", less consonant intervals, whose frequency ratios are expressed with higher numbers, were recognized. The presence of higher harmonics makes them sound less "perfect" to the ear, I suppose.

Dave

On Jun 2, 2011, at 2:53 PM, Richard Hunter wrote:

> John Neff wrote:
> <
> <This is the most basic definition:
> etc.
> 
> --which is good information, but doesn't answer the question posed in the title, which is not "what is a perfect 5th?" but "why is it called perfect?"
> 
> My wife once asked me why a "mole"--in scientific terms, a certain quantity of molecules--is called a mole.  The answer is: a mole is a certain quantity of molecules by definition.   
> 
> So the answer to this question is: a perfect 5th is 7 half-steps, by definition.  A perfect 4th is 5 half-steps, by definition. 
> 
> As to why the term "perfect" was chosen instead of something else, I suppose it might be possible to find the first use of the term in some medieval text, maybe even along with an explanation (which given the liturgical nature of early music would probably have something to do with these intervals sounding heavenly, especially in the temperaments commonly used at the time)--but that's a job for musicologists, not musicians.  
> 
> Thanks, Richard Hunter