Why are birds never out of key when they sing?

Question

Why are birds never out of key when they sing?

In fact, this is not just about birds; almost all creatures that make pleasant sounds (except us) never make a note out of key.

How is this possible?

Answer 1

Birds don't sing in a key. Keys are human cultural constructions with some basis in physics, but primarily just artful constructions of a sentient mind.

In fact, when you hear a parrot or something similar attempt to mimic human song, it's not nearly as "in key" as even an average human singer would be.

Birdsong only sounds pleasant because you've learned to associate the sound of birdsong with pleasant things. This is clearly not uncommon! But don't confuse "pleasant-sounding" with "in key." They are NOT the same. A babbling brook, I might say, is a pleasant sound--but it's not even something that can be easily defined in pitch.

Now, what you may be hearing are recognizable intervals between notes being sounded by what I'd call a monophonic pitched songbird. It might be possible to interpret groups of these notes as if they were in a key, and in fact some composers are known to do this (see Olivier Messiaen). However, intervals between pairs of notes don't put birdsong into a key, since every next interval is going to imply something totally different. The intervals themselves are probably based on the harmonic series (since that's the easiest way for physics to work), which is a shared root attribute of human cultural tonality, hence why those notes can sounds like they're "in key".

Answer 2

Bird song is not tonal. Read this paper by Wallins and Mercer. A key quote from them:

Any similarity between birdsong and modern music is by analogy

And Carol Whaling (document available at the same link) provides this spectral plot:

Which you can see is not tonal, in the way we think of music.

Answer 3

I'm happy to admit that I don't know what I'm talking about on this subject but its my understanding that all creatures that rely to some extent on sonic communication occupy very select frequencies on the global soundscape.

i.e. Elephants use very low bass frequencies to communicate, whales very high frequencies. It depends on the medium in which the animals exist i.e. air or water etc.

Birds themselves communicate on different bandwidths of frequency.

A sparrow for instance communicates sings on a bandwidth that is distinct from say, a magpie. This is so when they all occupy the same space they can differentiate the calls of their own species from that of others i.e. increase the signal to noise ratio.

No doubt their hearing is specifically attuned to these frequencies as well. I'm not saying they're deaf to other frequencies but that their hearing is geared towards a specific range of frequencies as is our own.

So when you ask how is this possible. Evolution no doubt. I'm sure their lyranx or tweeters or whatever you call a birds voice box is engineered to produce certain frequencies in much the same way as tuning a guitar... by tensioning the strings.

In other words its possible because its necessary to survive. If birds couldn't call a mate or hear the cries of their young when in a forest full of different bird species, they'd simply perish.

I don't know when the last time was that you were in a forest but them birds, they sure do make a racket. They're always talking over the top of one another. So without "perfect pitch" they may as well be talking to themselves.