My personal opinion is that we have lost NOTHING. The trumpet has been evolving/transforming about every 50 years and that the issue is more about what the contemporary view of what is acceptable. The end of the baroque era brought the requirements of chromatics that the natural trumpet could not fulfill. An additional handicap was classical modulation of the key signature that ruled out "mean tone" instruments. Initial attempts to get the trumpet chromatic sounded HORRIBLE, that resulted in it losing its "solo instrument" position in the orchestra and it wasn't until the late 1800s until further developments enabled the trumpeter to recapture melodic superiority. With the advent of recording technology, the requirement of security drove the creation of shorter instruments (in Bb, C, D and Eb). In Germany around 1900 the Bb trumpet common today was called the "high Bb" trumpet and the orchestral players using the deep F trumpets commented on the thin sound and lack of color of those Bb instruments. They lost the battle.
Rediscovery of Bach in the 1920s and 1930s drove development of smaller bore high D, Eb, F and G trumpets. Jazz drove additional changes to the Bb as did raising concert pitch to A=440. Charles Mager bringing french C trumpets to Boston was an additional change. After the second world war, the volume war started. Symphony orchestras (especially the brass) got larger bore instruments to get a "darker" sound that fitted in the orchestral fabric better. Unfortunately, that development increased the loudness, driving orchestral pitch up to the current A=442/443 to make the woodwinds brighter to compete. The string sections got strings that were also much louder.
Now, to get back to my original premise: trumpeters never had any need to ignore history or lose certain playing techniques. This was and still is their own choice. I listen to recent symphonic brass recordings of Gabrielli and wonder why nothing has improved since the 1960s when Philadelphia, Cleveland and Chicago created their legendary recordings. The reason is choice and ignorance. Ed Tarr and many others have made historical performance practice popular and accessible. Choosing to ignore what has been learned is my definition of ignorant. There is NO REASON FOR A MODERN PLAYER TO NOT ENCOMPASS THE ORIGINAL INTENT OF COMPOSERS FROM ANY ERA. Everything is freely available in our information age. I do not need a cornetto to play Gabrielli or a natural trumpet to play Bach. I do need to understand performance practice, pohrasing, articulation and blend to serve the original intent however. It is there for the taking as long as we are not too proud to bend over and pick it up!
We can learn a lot from these pioneers.
