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The video below is entitled "The Power of the Pentatonic Scale". And from the video you'd think that people are inherently tuned to the pentatonic scale. But I was wondering if they're really inherently tuned or did Bobby tune them? Could they have just been easily tuned to the major scale (or even minor scale)?

In the video the C# pentatonic consists of the notes C# D# F (aka E#) G# A#

at 0:19 he jumps on the note of C# a few times to establish the root

at 0:33 he jumps on the note of D#

at 0:42 the crowd correctly guesses the F. which is kind of cool but it makes sense since it could be the major scale.
at 1:06 he jumps on the pitch of A#

he then plays on A#, C#, D#, F for awhile

at 1:56 the crowd correctly guesses G# (which is amazing)
at 2:02 the crowd correctly guesses F (which is super amazing bc they figured out it was pentatonic)

at 2:05 the crowd correctly guesses D#

at 2:07 the crowd correctly guesses the tonic of C#

So my question is if at 1:06 had he jumped to the seventh of the scale (C) instead of A#, would that have made the crowd guess the major scale instead of pentatonic? It's not like humans are just about pentatonic right?

Humans are pattern-seeking primates. And within Western culture, we have all internalized, consciously or not, the patterns of the major scale and pentatonic scale, because they're commonly used in folk songs and children's tunes.

Once Bobby jumps to that A♯ at 1:06, the audience recognizes the pitches not as the entire major scale, but as the specific subset of it known as the pentatonic collection. (Again, this recognition can be conscious or subconscious.) From there, the audience is able to guess G♯ as the next lowest note, followed by E♯ below that.

Had he jumped to a B♯ at 1:06 instead, their brains would have recognized it as the major scale, and they would have almost certainly sung down that scale, instead.

It is cool that the crowd "guesses" G♯ at 1:56, but it's to be expected. With what we know of our brains' key-finding algorithms, it's one of the few choices available to us. We want to sing something that "fits" with the pitches already presented, and we tend to favor smaller steps instead of larger leaps. And since the audience has been primed to accept C♯ as tonic, they wouldn't have sung a G♮ or A♮, because those don't fit into any common scale patterns built on C♯.

Keep in mind too that there may be some strength in numbers here. Audience members with more musical education probably sang more confidently than those that view themselves as "tone deaf." So when a new pitch came, I would bet some members suddenly went very quiet until they heard what their neighbors were singing. But that's just speculation.

The crowd catch on quickly. But he cues them pretty strongly by singing the notes while setting up the pentatonic scale, and at 1'06" he definitely teaches the crowd what he wants. There's a similar demonstration online where he has to insist pretty strongly that he wants a ♭7 rather than a leading note.

He's got a point. He's got a lot of charisma. But yes, I think he could have done a similar demonstration (to a Western audience, at any rate) with a major scale.