Colin's hit the nail on the head. As a w/w player and with experience in many ensembles of many sizes, the 'collective' gasp of taking a breath after a particularly long or sustained passage can clearly be heard within the orchestra. As a rule, and maybe for orchestrative reasons, w/w tend to get more work, which means you would think they're louder in the 'intake of breath' department. But there is a clear difference between the human intake with virtually no resonant response from w/w, versus the audible intake from Brass players, whose intake is enhanced by the 'echo' of tubing.
A busy and challenging brass part is inflected with this resonance, and it's just one reason why the 'live' sound is so complex, and not easy to attain.
3 Trombones all breathing in at the same time to play a fanfare or sustained loud note, have this 'pre sound' at a noticable level. Whether you class intake of breath as pitch orientated or percussive is up to you, but this 'human sound' is as much part of a live performance as anything else.
String players are no different, and during complex passages, particularly tremolos, they have a habit of almost grunting whilst playing, and an sometimes audible exhalation after the passage has ensued. This is of course general, and in quiet passages, players are a lot more careful about sort of extra noises they make.
So the notes you write with samples, start and finish precisely where you place them. In a live scenario, there are 'pre and post sounds' that create that human edge we work to attain, and in the pursuit of a live sound these should be taken into consideration.
As an addition to this, there are many percussion players who quietly 'test' their instrument or pitch just before playing it. Although the sound may not neccessarily be audible, it does register and contribute to the overall sense of 'living' that is attibuted to a live sound.
Then there's the additional sounds of mechanical manipulation of an instrument. The clarinets, e.g. going from a middle C down to E (written) will have to cover the three holes with the right hand, and operate additional side keys. In a slow passage this mechanical movement would be almost silent, but in faster or more strident passages, this sound will be heard, at least within the surrounding area. Likewise trumpets and horns, when playing intervals involving the use of pistons and valves will create some noise too, enhanced once again by the 'echo' of tubing. This is far more apparent in quicker passages than slow, but the ffect remains, especially in quiet, quick passages.
The live sound is a collection of various noises both human and mechanical, so adding breath to a track is only one part of the greater whole. Incidentally William raised a good point in another thread about producing a sample performed work. The discussion included the possibility of respectibility for composing in this manner, and the acceptability of sampled versus live performance. Maybe this discussion about live additions to work should be considered from this perspective too. After all, i can guess a large chunk of today's film music is performed with samples.
Do they include the 'live' sounds, and are they really necessary?
What's the goal? An imitation of a live performance, or a work written with the intent of a sample based performance? There's a perception that sample based work is somehow inferior to using a live ensemble. This may or may not be true for the majority of the public, although i suspect many wouldn't know the difference if the work was well 'performed'. But, given the superb libraries of sound we have today, the respectability of samples versus live should be re examined.
(IMO)
Regards to you all,
Alex