Could you use this for, say, a dance performance?

That’s happened in almost every unaccompanied chorus I’ve ever been in…

Also, to Andremount #41 – Thanks for explaining the details of situation thoroughly and for adding in your expertise!

The ratios in a scale don’t add, they multiply. This means that dividing an octave (with a 2:1 ratio) into 12 equal pieces results in a semitone ratio which is the twelfth root of two – an irrational number – so that all intervals except unison and octave are to some extent dissonant.

Tempering this to something that sounds good in a variety of commonly-used keys is the real trick in tuning theory and practice.

Thank you. To me, half the “wonder and awe” of this whole thing is in the audience being able to kinda approximately predict the pentatonic scale with a bunch of clues. There is some sort of bias in the prediction of the scale.

The other half of the awe and wonder is how everyone who views the video further inserts even more bias into the listening act — kinda approximately telling themselves what they’re hearing.

There’s just as much bias going into an audience predicting pentatonic scale as there is in getting us BoingBoing commenters to believe we heard some perfect notes.

The layers of perception bias here are even more fascinating than just the video.

Interesting that an auditorium full of strangers can spontaneously form something so fine, not from practice or because they have been carefully selected, but just because they are people. A small amount of a certain kind of leadership was all it took to bring forth that happy averaging of voices to produce music, and to make each contributor a good singer.

We should have elected Bobby Ferrin in 2000.

Except that the ratios aren’t whole numbers. They can’t be, since no matter which tone you start at, the octave above is 2x the frequency. Rather, the frequency ratio of adjacent semitones is the twelfth root of two.

I stand in gobsmacked awe of those commenters who presume to call out McFerrin for using shills. Not because it’s demeaning, but because it would make NO DAMN DIFFERENCE! To think that it would is to totally, utterly, absolutely miss the point. It is singularly obtuse.

This demo is precisely the sort of effect than cannot be shilled. Shills or no shills, what is happening is the same: each audience member is choosing a note to sing based on what they initially guess and subsequently hear. The process by which the (roughly) correct note arises is what’s wonderful, and that process would be unaffected by the presence of a few shills who sing on key. Individuals with good pitch will be present in any decent-sized crowd anyway. People’s SENSE of what pitch is correct is the cool part. A few shills singing the correct note would not help anyone make the correct choice–everyone could just as easily choose to IGNORE the shills, UNLESS they already have a sense of the right pitch, which is THE WHOLE DAMN POINT!!!!

Shill accusers: you FAIL. Horribly. Miserably. Totally.

(Not to mention, it IS insulting to McFerrin, and anybody with a functioning mind.)

Moving on, I enjoyed this display of Mr. McFerrin’s experiment. It geared me to think about many things which I will now read up on. Thank you for sharing, Cory Doctorow.

I’d love to see the subsequent discussion. Do all audiences do this because they’ve been acculturated to do so, or is there a way that our brains are wired to “think pentatonic”?

Now the pentatonic scale is simply the easiest ratios you can find inside the 12-tone scale. the central note here, one that you can tell he likes to end on, is the note that people in this thread have assigned the name II.
A fifth above that is the note he introduced fourth, a fifth above that is the note he introduced third, the fifth below II is the note he let the audience figure out, the fifth note introduced, and a fifth below that is the first note he gave.
It’s the nicest whole number ratios you can make in five notes, which is why it shows up everywhere. So the genetic reason you are searching for is not some evolutionary reason to use the particular scale, but rather an appreciation for the underlying math of music that has been given to us through evolution.
As to why we subconsciously enjoy simple whole number ratios in things that we hear, I can’t provide the evolutionary reason for that.

Maybe God put the ability to find pleasant things into the human senses on purpose, because He desires us to find pleasure in the creation, including in ourselves. And evolution didn’t cause the development of what seems pleasant to us, because God delights in us and wants us to delight in Him and His creation.