Very much a music amateur here, primarily at home for personal enjoyment and now in a race against time re arthritis. Rarely in public - there was a time I performed with our local music club concerts but it was usually more stressful than fun. The box bass is great fun jamming - but I suspect I rely on getting near enough to the right pitch, or just being headed towards it makes it sound 'right' rather than actually getting it just right. Yet I am confident that whatever the tuning I start with (playing alone) I can maintain. Don't have perfect pitch, but I do wonder if by remembering a well known tune I can recall the correct pitch for the key that goes with it? If so, could a lot of people, more than we think, learn to have perfect pitch? (Getting yet further off topic here, just something I've wondered.)
Keys having emotional 'flavors' ? They never seem like that to me. The relative differences between notes - the intervals as arpeggio or as paired notes and chords - do seem to have emotional flavors. The changes between chords seem to have flavors. Why those combinations do that - and do it similarly in different people - remains a mystery to me. But I don't need to understand it to enjoy it.
Birdsong? I am quite fortunate for the range of bird life where I live (rural Eastern Australia). I am aware of one songwriter who has written songs built around Australian bird melodies. I have occasionally noticed a call that sounds like two (rising) notes sung simultaneously - without managing to get a clear look to identify the bird. That is the only birdcall I have noticed that is like that. My 'ear' is not good enough to identify the kind of interval it uses. We get some remarkable bird duets too, notably from the Noisy Friarbird.
I must say I think the notion of keys having different flavours is all balls. Different modes yes, but not different keys in the same mode, e.g G major vs. C major.
The only basis I can see for this idea of keys having flavours is due to orchestration. For instance the open strings on the violin are G, D, A and E. All other pitches involve stopping by the fingers. There is certain extra sonority to an open string, which might give, say, the keynote chords in G major an extra depth - on the violins. Here's an example, Agnus Dei from Bach's B Minor Mass:
This is in G minor. A lot of resonance from the bottom Gs which give it a certain groundedness, in spite of the ethereal, chromatic nature of the melody and harmonisation (the score is full of accidentals). There is also a G string on the cello, so you get the effect in the bass as well. But this would not apply to other instruments, and certainly not to an equal temperament keyboard instrument.
Another example is D major which, before the valved trumpet, was the key all trumpet music more or less had to be in, hence its prevalence in triumphant or military pieces in Baroque music. (Bach uses a high F trumpet in the 2nd Brandenburg, but that seems to be unusual and must be a bastard to play.)
I suppose historically, in the days before equal temperament, different keys
would have had rather different qualities, to the point of weirdness if one strayed too far from the "home key" of C. But anything post Bach (1750) would have been equal temperament so that would not any longer have been true. If you want a laugh, listen to this:
Christopher Hogwood playing an alternative (and I use the term advisedly!) Allemande from Bach's E♭ major French Suite, on a harpsichord tuned to one of the many non-equal temperaments of Bach's time. The further from the home key it gets the more strange and discordant it sounds. There is a palpable sense of relief when it comes home again. I can imagine Anna Magdalena wincing and saying : No dear, I don't think your public is quite ready for that."
