eli5 How does the brain separate out frequencies it’s hearing so that we can make out different instruments in a song? It seems like some insanely complex analysis behind the scenes??

Question

eli5 How does the brain separate out frequencies it’s hearing so that we can make out different instruments in a song? It seems like some insanely complex analysis behind the scenes??

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Answer 1

You are correct, it is insanely complicated and we still don’t understand it completely.

It’s important to understand that what you perceive is not the same as what’s physically there. You hear one sound (e.g. a piano playing), but it’s not just one frequency that is produced by the piano. Instead you have the [fundamental frequency ](https://en.m.wikipedia.org/wiki/Fundamental_frequency) and then there’s even more frequencies, the [harmonics](https://en.m.wikipedia.org/wiki/Harmonic), where the waves overlap.

So even if you consciously hear only one specific tone, in reality your brain receives a pattern of frequencies and just tells you that you hear one sound instead of a multitude of sounds.

The harmonics influence the musical timbre or tone quality of the sound. Thanks to that, when hear a piano and a guitar play the same pitch, you can differentiate if the sound originated from a guitar or from a piano.

So that’s what your brain basically does. It listens to the sound it hears, analyses the frequencies of the fundamental and harmonics and can then not only determine the pitch of the sound but also the instrument.