First of all let me refer to my website page on the difference between loud and carrying.
Let us consider the following before going into the dynamics subject as such. Why did the conical flute win over the recorder? I think that one of the most important reasons was the fact that we can play loud and soft on the flute and stay in tune easily! Therefore playing both loud and soft must have been used at the time. And most likely really both, loud as well as soft! It really must have been a discovery to be explored.
I am using the word loud in the following because I think that that is what players in this issue focus on but I actually think that carrying is more important.
I would like to introduce the term "dynamic equilibrium"**. It is a characteristic of the instrument. (definition below but just forget about any formal usage)
I found that everybody understands intuitively what I mean by dynamic equilibrium in the middle.
I have the impression that players now often want flutes that are immediately loud (high dynamic equilibrium). Immediately in the sense that when they just play for what might have given little noise they already get much. So on such instruments one has to work to play softly. But who cares is the idea because this would make it easier to be heard in an orchestra.
The misunderstanding is that then they will actually be louder then the regular eighteenth century original also when that original is played loud. I believe that this is not really the case. Also it does not mean the flute carries better!! The last is of course really important.
As an example, Isabelle Lamfalussy plays one of my Beukers flute next to Marion Moonen who plays a well known Palanca and is a superb player of course. Isabelle has no problem being equally loud. She knows how to do it. I know quite a number of players who easily do the same. On the Beukers it is equally easy to play very soft, the tone will stay with minimal breath.
All eighteenth century originals I know do not have the "immediately loud" property, including the original Plalanca's I know (copies are mostly used for immediate loudness).
Originals practically always have the dynamic equilibrium in the middle (until the end of the eighteenth century). So equal effort for playing piano and forte.
It is important in this context to stress that originals and good copies of originals almost always can be played loud as well as soft. And especially they can be played to carry! Of course large modern concert halls and big churches give problems for some music that simple is too much for any traverso. But then, modern electronics ??
However, there is culture of not using the dynamics of traverso on the loud side because there are some much celebrated originals that do not have it! Some even more celebrated teachers have taught to avoid the loud side of the dynamics because they love those originals. Because they are super celebrated teachers they have caused a culture of no attention to playing loud on a traverso that has that possibility. A further reasoning was that if these celebrated originals do not have the possibility of playing loud playing loud was simply not done in the eighteenth century. However being heard is essential for the modern player of course and most likely has been often in the eighteenth century as well!! These originals do not have the loud side now but whether they did not have it originally is for me also a question mark.
Of course it is very well possible that there were instruments meant to be used in small environments. Maybe in court a small room was used with a small audience and those flutes were especially good for this. However, churches also in the eighteenth century were large spaces. So more power was necessary also then.
Historically one could say that there has been a period where, because of the influence of those celebrated players playing loud was out. As a reaction on that we have seen that only loud also became a goal as such. This maybe still is found quite a bit but I believe that using the dynamics of the traverso from piano to forte should be normal. Especially in recordings there is no reason not to use the whole gamma.
Of course playing loud on a traverso should not be compared with the relative ease of making a lot of noise on a Boehm flute. However, given the right technique it is quite possible to make a bit of noise on a traverso as well. This technique however really needs some special attention. I think that it might be informative to study the way dynamics are used on the recorder by players of the Dutch school. For some time I played recorder (no good) myself and remember only how my teachers stressed using body resonance instead of blowing hard or soft. Of course this is more clear with a recorder than with a traverso because on a recorder blowing hard or soft immediately makes the tone higher or lower. So, that can not be done. Instead using body resonance is the only way. But this technique together with the breath pressure possibilities makes the traverso a far more dynamically flexible instrument. For more knowledge on body resonance one should go to the singers world. It is far too much to start discussing it here. Lots of knowledge there though!!
I am not a professional player though so these are remarks by an amateur listening and looking only!
Of course all knowledgeable players know that the loud side of the dynamics of a traverso must not be used by just blowing harder!! I am just mentioning this to prevent any misunderstanding.
To prevent any further misunderstandings, I love listening to the superb players who are not particularly interested in using the loud dynamics on the traverso.
**Defining this is a bit a scientists game. I am doing it because I would like it to be defined but I will talk about it intuitively because I think that most players will understand what I mean. It is the ratio of the effort needed to play piano and forte on a traverso. So if this is low you need effort to play forte and you need little effort to play piano. If it is high you need much effort to play piano and little effort to play forte. I am not going to quantify this any further except for the value 1 which gives equal effort for piano and for forte. This I will call dynamic equilibrium in the middle.