What’s an Octave?

An octave is an interval in music.  The concept forms the basis of Western music’s notation – A B C D E F G A – 8 notes.  In this example, A and A are an octave apart.  Though we don’t know which “As” I’ve specified, we can know that, if written in ascending order, the A on the left is ½ the frequency of the A on the right.  For example, if the A on the right is my violin’s A string tuned to 440 Hz, then the A on the left represents a vibration of 220 Hz.  As far as definitions go, that’s really it – it’s about dividing or multiplying a base frequency by 2 (musical frequencies are logarithmic in origin).  We call it an octave because we divide the interval into 8 notes.

I’ve been trying to appreciate a “how” or a “why” for the octave for a while now.  Why does it sound perfect to humans?  Wikipedia reports that in behavioral experiments that monkeys respond in a knowing way to octaves as well.  Obviously the octave is a logarithmic nicety, but is there some biological basis to it?

Yes, apparently so.  That’s about all I’m going to be able to say on the subject without quite a bit more reading.  Martin Braun is a Swedish Neuroscientist, and he offers a history of discoveries related to the octave.  One such discovery is a physical correspondence between musical perception and the thickness of the regular groupings of neurons in the auditory thalamus of mammals.  In other words, mammals seem hard wired to perceive something special in an octave.  The neurological patterns have been shown in both rabbits and cats.

There’s something quite fundamental about vibration in our universe – I’m enjoying chipping away at the concept.

Thanks for reading.

Ryan

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