I recall reading – probably on Wikipedia – that spring-tempered bronze was in fact a thing. It was in relation to the ancient Greeks, I think, but I don’t know what article that might have been.
Otherwise, refer to this:
Also, I recall a thread on the old forum, referring to “bronze longswords,” which referenced some of the very long Chinese bronze swords. It’s possible these would have had to have been spring tempered to function without breakage.
Now, to contrast the Carnyx, you’ll have to have a Roman horn: