parallel major thirds

Carl Lumma quoted others:
>>>I saw a post on Usenet recently where somebody said that parallel major
>>>thirds increase the tension.
>>
>>Parallel _major_ thirds would be a very non-diatonic phenomenon (q.v. _Close
>>to the Edge_ by Yes) and increase tension due to its borrowing from distant
>>keys.

And responded:
>
> Woohoo!

Evidently, this conversation has overlooked the fact that the _diatonic_
major thirds in the IV and V chords are often sounded in a parallel manner
in the IV-V chord progression. Even when the other chord members are not
present this combination of major thirds not only creates harmonic tension
but actually _defines_ the tonality. (This characteristic only happens
diatonically in that location in a major key.) That is why the functional
tritone (whether sounded harmonically or, in this case, melodically) is so
important to creating the musical energy in the major/minor system.
>
>>In normal music, thirds are hidden away inside chords. For virtually all
>>music written since the demise of meantone, this is true.
>
> Uh? What about melodies harmonized in thirds? 6ths are maybe more common,
> but....

Thirds and sixths are equally common. Note that one is the inversion of the
other. It's the "same thing" upside down. Usually, however, melodies
"harmonized in thirds" mix major and minor intervals that normally reinforce
the tonality.

Supplied only for "what it's worth." :-)

Jerry