Sometimes, singing in tight vocal harmony, certain chords locked just right will produce a hair-raising effect: the air buzzes, the sound gets "fuller," goosebumps, psychosomatic tears. I think it comes from overtone overlaps? Sharing rabbit hole and questions so far:
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Combination tones. Hindemith wrote about them in "Craft of Musical Composition."
If I sing frequency A while you sing lower frequency B, then the first-order combination tone produced is frequency (A-B).
Perfect 5th reinforces the bottom note, P4th the top (but octaves down).
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Isn’t another name for that “beat frequency” ? Or are you talking about something different.
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Same principle, but in this case the beat frequency is so fast (and specific) that it generates physical pitches, in tune with the existing interval.
I think of beat frequency as a several-per-second thing that I use to tune my strings into purer fifths.
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I think it's also different insofar as combination tones are claimed to be a psychoacoustic phenomenon. That is, it's not that the beats physically produce a pitch, but that you *perceive* an implied but absent pitch. (I may have this wrong though!)
Yeah, that surprised me a bit too, as I read it. Combination tones show up in recorded sound, which I guess isn't necessarily dispositive either way!
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Ah thanks! Sounds (ha) like it is believed to be due to auditory system non-linearities:
szhorvat.net/pelican/combin
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