Tonal Markings For Brass

Well, I'm only familiar with brass samples...and the crossfade.  I've read Adler's orchestration, and I didn't see anything regarding this. 

How do I mark a mellow timbre fading into a rich, resonant one...Is this just a regular dynamic marking, for instance, p < f > mp

Where sheer dynamic control changes the timbre in this way?  What I am asking is:  can I change the timbre from mellow to rich, without changing loudness/dynamics, and without stopping?....or what about playing a sustained note, and slowly adding the mute to the bell, throughout the sustain.  Is there a marking for it?

Any ideas?

You could indicate it as a performance direction.

yes p < f will imply brighter sound, real instruments are not like samples, that you can just turn up volume using a pp sample, in real life if you blow more, it will sound louder AND brighter.

Great answers!

In general, the softer you notate a brass instrument to play, the less timbre-change is available.  The louder, the more you have to play with.  Timbre quality is generally notated as text above the staff.  For example, Brassy! is a common notation, letting the player know to somewhat overblow so the bell of the instrument rings with an edginess to it.  Similarly, in French Horn music the notation Bells Up is a common way to say to the horn players "I want people on the other side of the world to hear you!"  Still, the options for timbre are limited.  Generally speaking, the timbre is controlled by the amount of air being forced through the instrument (the dynamic marking).  Slurs, dynamic markings, and articulation marks have the most impact on the sound/timbre coming out of the instrument:

• > = Accent the beginning of the note
• sfz = Really accent the beginning of the note (you can even exagerate this with sffz)
• fp = hit the note at forte, but then back way off to piano
• . = stacatto; play the note short (often about half the length written--often used simply to add separation between notes, helping accent subphrases without actually accenting notes!)
• _ = legato; almost slur the note into the following note (you still tongue the next note, however) -- this does generally have the effect of making the tome more mellow
• > with _ = Accent the start of the note making it a bell tone--very common in brass

There are a myriad examples of how a composer can subtly give clues to the performer on what the intended sound should be.  Remember, if all else fails, you can simply write above the staff the sound you are going for (e.g., distant sounding or brassy!).  I would highly recommend that you study some brass scores with a recording of it next to you as you analyze the score.

Thanks to everyone!  I think I know what to do now.  FossMa, thanks your information as well...I will put it to use.

I'd recommend Norman Del Mar's 'Anatomy of the Orchestra'. Its denser than the Adler but in turn provides much more information, particularly of less common techniques. Which Adler sometimes omits.
If I had my copy with me i'd have a look in the Brass section of it now, but i've left it at uni.