Part of the problem with describing this on the horn is that none of it is very visible. For stringed instruments, there are obvious externally visible changes you can make. These include:
- Playing at the heel of the bow or at the tip
- The width and speed of your vibrato
- How close to the bridge you have the bow
- How much pressure on the string you have
- What speed you move the bow
- Which string you play on
- What angle you hold the bow - affecting how much hair of the bow is touching the string.
Similarly, there is a surprisingly wide range of tones you can get from percussion instruments such as the timpani. Here, you can change tone by means including the following
- The type of drumstick you use - you get great variation in tone from differences in weight, material and hardness.
- Where you strike the drum - different distances from the edge can have quite different effects
- The manner in which you make the stroke - what speed and weight you put into it
The point is that the techniques are visible, and have a vocabulary associated with the actions you take to achieve a tone, so it is relatively easy for both string and percussion players both to talk about tone techniques to each other, and to teach them from a relatively early age.
But it is a bit different for wind instruments. The techniques for changing tone colour do exist, but they aren't visible. They consist of changes in air support, in minute changes of muscle position and tension, and for the horn changes of the position of the hand in the bell. It is far harder to say "change such and so by this amount to change the tone in that way", because neither the teacher nor the pupil can see what is going on. Because the changes aren't visible, they are visualised instead, and often quite inaccurately.
This has bedevilled the teaching of wind instruments for ever. And as a result, the common vocabulary has tended to grow up not so much about techniques, but rather about effects. Wind players have a range of words they use to describe subtle differences in tone colour, in much the same way as the Inuit have many different words describe different varieties of snow.
But there are some things you can say. On the horn for instance, having the right hand closing the aperture of the bell a little more produces a darker, more velvety tone, whereas opening the right hand produces a brighter sound. Tightening the lips and reducing the aperture, and increasing the air pressure to compensate trends to produce a more "brassy" edge to the sound, whereas relaxing the muscles a bit and allowing more airflow with less pressure tends to produce a more mellow "projected" sound.
And just as you can vary the attack as a string player by how you place the bow on the string, so you can do the same in wind playing, by how you tongue a note. You can vary where on the roof of the mouth the tongue rests, how fast you move it, and how much of an excess of air pressure you allow to build up behind the tongue. All of these things will affect how the start of the note sounds.
Each wind instrument has its own techniques. They tend to have a certain amount in common, in that they are for the most part concerned with intimate control over air supply and embouchure. But the effects do vary a significant amount from one instrument to the next, given the differences in the basic mechanics of sound production.
But the first and most important thing to realise is that you can gain conscious control over your tone, as distinct from control over your dynamics. You can decide how you sound as well as how loud. The second thing to realise is that differences sound much greater to you than they will sound to the audience having been attenuated by distance. So if you want variety of tone to feature in your repertoire of expression, then you need to be able to produce exaggerated changes. Only if the variation seems comically overdone to you will the audience be able to notice much of a difference at all.
Most professional horn players are well familiar with this, but I'm surprised at how many even quite good amateurs haven't quite grasped the concept of tone control and variation as a deliberate tool of expression.