Historic brass instrumentmaking: the what, how and wherefore:
The goal for today's early music specialist is to recreate, to resurrect the music of earlier eras, and in doing so to give our modern audiences an auditory window into the musical past. To do this, we need not only the right dots on the page, but also the right attitudes, knowledge, and tools. Whether a trombone, a violin, an organ, the instruments we use for recreating the music of the past influence how we play it.
If we're going to use "historical" instruments to play historical music, what is the point of going halfway, of making compromises? If we want to attempt to recreate a past sound aesthetic, how can we claim to do so using equipment that would surprise a musician of the period?
The answer is simple: we cannot.
Every compromise and modernisation today's early musician makes is a sacrifice of "authenticity" - and must be recognized as such, whether it be chromed trombone slides, vented "baroque" trumpets, or something as simple as a venturi at the throat of a mouthpiece.
When a trombonist takes a copy of a sixteenth-century mouthpiece and finds it challenging to play without splitting notes, the answer is not to change the mouthpiece, but to learn from it, just as violinists learn to articulate well on equal-tensioned gut strings or woodwind players discover the nuances of half-holes, forked fingerings and historical reeds. Nor is the answer for the Baroque trumpet player to have a natural instrument vented - thus making it un-natural, but rather to commit to a historically informed setup from start to finish - and from there to master the difficulties of accuracy, range and intonation the instrument presents. The result of this is an altered playing technique, adapted to the tools for the job, and in turn to the music at hand. Perhaps the learning curve will be steeper, the first stages more difficult, but the resultant insight and flexibility merit the added effort.
A vocal approach to instrumental playing
Since much of the music of the Renaissance and Baroque has its roots in vocal music, and much of our repertoire calls upon us to mesh with, accompany, or imitate the human voice, we must also take the approach of a singer when interpreting this music. This means attention to text, to color, to the shape and direction of each phrase, and to every possible rhetorical nuance; period sources support this sort of vocal approach. But what does this mean for the technical demands of this music for brass players in particular?
The starting point is colla parte practice, where instruments double the voices. Our job in this instance is to reinforce the voice, not only with added sonic presence, but also emphasis of the text. We have to play the words. Of course, dynamics and articulation are two of the necessary tools, but if we can furthermore change the sound color to match the vowels, we can further reinforce the musical rhetoric. A historically built instrument as a rule sacrifices consistency of sound for flexibility of sound color, of dynamics (especially at the softer end of the spectrum), of articulation... It provides a greater palette for artful, nuanced performance. The challenge of a less "stable" instrument is entirely worth the greater spectrum such an instrument offers.
Airiness turning to resonance
My experience over years of playing and experimenting has shown that a more flexible, transparent sound, even with significant presence of air or hiss, is transformed in a large church acoustic to clarity and presence without muddying a polyphonic texture. I believe that Renaissance and Baroque brass instruments need some air in the sound. To eliminate the hiss is to remove what turns into a beautiful, overtone-rich resonance in the context of ensemble music in a live acoustic. (These instruments were anyhow not intended for modern, dry concert and recital halls.)
In the context of the alta capella, a setup which at lower volumes produces some hiss tends to turn quite brash and brilliant, again with a fuller overtone structure which then meshes well with shawms and bombards, whereas a darker, airless (i.e. compromised toward modern norms) sound is more problematic both in terms of blend and ease of intonation. Furthermore, the response of such a setup when pushed gives the player cues to articulate and phrase differently, meaningfully changing the manner of interpretation in a way that would not have been suggested by a compromised setup.