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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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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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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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Replying to
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!
Left: original chord, as recorded (performers tuned in just temperament)
Right: chord with each track retuned to 12TET
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Replying to
Super interesting thread! I've wondered about this, but have never explored possible technical reasons for it. For me, it's happened with specific people (my friend Amanda, for one), and I thought maybe our voices were similar enough in timbre that the vibrations…aligned well?😅
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Yeah, that sounds right! I think "mismatched" people can learn to match in this way: when I was music-directing an a cappella group, we'd do exercises in each rehearsal to match vowels and tone; it had the side effect of making this phenomenon happen more.
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