The association of musical keys with specific emotional or qualitative characteristic was fairly common prior to the 20th century. It was part of the shared cultural experience of those who made, performed and listened to music. When Mozart or Beethoven or Schubert wrote a piece in a Ab major, for example, they were well aware of this was the 'key of the grave' and knew that many in their audiences were as well. +++ HERE +++ is a list of the emotional affect of each musical key.

Jim,

It's always interesting to read different writers' takes on the concept of keys. Thanks for posting the link. I notice that this particular writer briefly mentions how our current tuning system of 'equal temperament' has reduced the emotional impact of different keys.

The tuning system 'equal temperament' was developed a few centuries ago as a way of making it possible keyed instruments (organ, piano, harpsichord, etc) to play in multiple keys. If my music history recollections are correct, prior to equal temperament, these instruments only really sounded good in keys up to 1 or 2 sharps/flats.

It's also worth noting that prior to the early 20th century, concert pitch was not formally set at A = 440 Hz. This means the key of C (or Db, D, Eb, etc.) that Beethoven heard did not sound the same as the key of C that we hear today.

https://en.wikipedia.org/wiki/Concert_pitch

Regards,
Noel

When you add horns, certain keys have distinctive sounds because horns have their own distinct nuances of tuning. For example, if you want something to sound bright, concert D is a reliable choice.