Even makers of really exceptional instruments, recognized by many players to have no peers, were absorbed into the growing colossus. Bach trumpets and trombones. Armstrong flutes. LeBlanc, only maker of extended range contrabass clarinet (and for a while, "octo-contra-alto" and "octo-contrabass" clarinets, for a long while the lowest wind instruments ever made. Selmer USA (NOT H. Selmer-Paris, thank whatever gods there might be). Only a few survive. Conn-Selmer is part of a larger conglomeration built around Steinway Corp. Whatever changes they make to band/wind instrument manufacturing will effect almost everybody, even if indirectly. All those debates in band class about which instruments were better are almost all moot now.
C. G. Conn started a band instrument company after the Civil War, after first making custom trumpet/cornet mouthpieces to accommodate a wartime injury to his lip. With lots of changes and improvements in the craft of instrument-making at the time (valved brass and saxophones were still expanding their roles, and other woodwinds were following the example of Theobald Boehm and A. Sax to modernize keywork, for example) that may have been THE absolutely ideal time to get into the business. Eventually along came the saxophone craze of the '20s, and Conn played into that well, with new inventions (Saxello, Conn-O-Sax, "mezzosoprano" saxophone (Sax's suggestion, but never implemented before) and lots of P.R., including the construction of at least two giant saxophones, one a huge model of an alto sax, the other a working subcontrabass saxophone. Then came The Depression. Then came WWII, when brass for shells became a strategic material (bye-bye, subcontrabass sax) and instrument mfgrs shut down. After the war they and other instrument makers rebounded, and several different brands stamped their products "Elkhart, Indiana" where so many instruments were made, with a huge population of specialized workers in the area. There have been a few startups in the 20th century to take advantage of that. But then "consolidation" set in, driven by the go-go stock market of the '80s, when mergers and acquisitions were indulged in so recklessly, damn the company traditions that were destroyed in the process.
There were actually a lot of other things in between, including Conn incubating workmen such as Beuscher and Holton who went on to their own companies, switching almost entirely to electronic organs(!) and virtually ceasing to be an instruments manufacturer before being bought up and hammered into a conglomerate of other historic brands. C.G. Conn even served as a member of Congress at one point!
All fading into history now.