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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Unfortunately, it's hard to convey this effect with a recording—it's much stronger if you're producing it. So I guess I'm mostly talking to other vocalists.
The first key bit seems to be that voices can sing in just intonation, i.e. whole number ratios:
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(I'm totally skipping explanation of overtones, temperament, and the harmonic series here… for a wonderful intro, see 's youtube.com/watch?v=i_0DXx)
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In four-part harmony, singing the harmonic series 1, 3, 4, 5 can produce one form of this effect: i.e. the tonic, and its major triad in second inversion an above.
e.g. this (remarkable) cadence resolves to that disposition in A major (A E A C#): youtu.be/Qo_N9_ZFBhs?t= Tingly!
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I think it feels tingly because of all the overtone interactions between those whole numbers. The bass's overtones reinforce all the other fundamentals; then there'll be strong overlaps at 12, 15, 20, etc.
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In my experience, this effect is much stronger when singing with less vibrato and quite a bright timbre (i.e. more upper overtones!). I hadn't really understood this—I sing mostly contemporary pop—but barbershop stylistic choices are mostly in pursuit of this effect.
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They lean heavily on dominant sevenths, which (tuned in just temperament) are the 4, 5, 6, and 7th harmonics of a root two octaves down. en.wikipedia.org/wiki/Harmonic_ Lots of interesting overtone interactions create an angelic "fifth voice" singing high above! "Ringing chords".
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How do inversions/dispositions influence the effect?
eg If the Notre Dame cadence resolved to root triad instead of second inv above bass: 1, 2, 5/2, 3 instead of 1, 3, 4, 5. That'd emphasize a root-fifth interaction, which might detract from the sus resolution of the third.
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I experience something like this effect with close dissonant chords, too, which barbershop eschews. What's going on there?
e.g. in Eric Whitacre's music, there are lots of so-called "fist chords". These sometimes produce the effect for me too! Why? Overtones aren't very aligned.
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Why is this effect so much stronger for the singer than for the listener?
There's something in being the *causer*, but it's also physical: when the effect occurs, It feels like my voice, my chest, the air in my lungs, my muscles, all resonate with the room and the other singers.
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Why is this physical sensation so powerful?
It feels almost overwhelming sometimes! Like being given over to a "higher power" for a moment. It's beautiful, moving… and a little eerie. Why do we respond this way? Odd!
"Sense and Sensation in Barbershop": jstor.org.sci-hub.se/stable/41700111
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Goofy question I've been noodling with: it's not easy for an amateur to produce this effect—so could one design a simple cybernetic exhibit to give an untrained person the experience of causing this with their voice? I have a few ideas…
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This feels like a dumb question, but: why don't we notice *destructive* interference more in vocal harmony? This figure shows constructive interference in a harmonic seventh chord—but that assumes everyone's in phase! Which… they won't be, right? Do we instinctively auto-align?
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Related, important: vm.tiktok.com/ZM8bkaJ4J/
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Very interesting replies from suggests that the overtones are a red herring, and the "expanded sound" effects actually come from a phenomenon called "combination tones" (lots of back and forth in subtree):
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Replying to @andy_matuschak
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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A nice instance of the effect: twitter.com/andy_matuschak
I've noticed I can produce the effect alone by singing one part with a vocal recording of the others. It's better when I can find "practice" tracks which have "my" voice missing—I think because sloppy unisons mess it up.
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35 seconds on that high Ab, and so shimmery. Really hear an illusory fifth voice singing a high Db above the chord in the last few seconds. youtube.com/watch?v=Mmu-t8
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Experiment! I got a multitrack recording which has a mega-shimmery chord voiced as Db4 Ab4 Db5 F5 (ie partials 2-5 of implied Db3). It's tuned in just T, but I repitched each track to equal T… and the overtones are still amazing. So the effect doesn't strictly require just T!
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