Hi Tom - while you are correct that warmth, when describing timbre, can be very subjective, there are huge differences between different instruments, and players of the same instruments. A flugelhorn, for instance, is most certainly a warmer timbre generally speaking than that of a trumpet or cornet. Miles Davis had a warmer sound in general than Dizzy. This is not to say that Dizzy did not at times have a very warm timbre. This is not at all a simple thing - many factors go into it. Speaking of brass instruments, the alloy the instrument is made of has much to do with it, as does the design of the instrument, as does the mouthpiece used to play it. In the case of the horn, my instrument, the position of the player's hand in the bell of the instrument has a great effect on the timbre. The way the player's airstream moves into the instrument, and the way the player's embouchre is formed (the position of the lips and the manner in which they buzz or vibrate) and manipulated have a very great effect as well. All of us musicians are constantly working on our timbre production, and the variety of it, and warmth is definitely a word we use to describe it, and we would like an audio system to reproduce this quality. Unfortunately, even the very best recordings played back on the very best systems do not come close to capturing the minute variations in timbre that can be heard live in a good concert hall (speaking of which, the room itself of course has a great deal to do with the perception of warmth, and the room an audio system is in will also have a big part in the listener's perception of warmth).
