It wasn't until I think around the advent of recorded music and electric amplification that it settled into a fairly stable set of instruments & sounds produced by them.
The music of the classical canon is unbelievably fantastic, and it deserves respectful treatment, but the genre has lost the audience for cool new sounds. It’s very unfortunate.
It's simply not the role of any one musical practice to be at the forefront of experimentation forever. What we now call classical passed its torch on generations ago, and rock & jazz have now settled in too. We have hip hop and electronic music taking this role now, and eventually they will bind up into their own conventions and some descendant of theirs will push on.
This annoying behavior does not win me any friends but remember that the great classical composers were the rock stars of their day.
Hell, in a century you’ll see string quartets banging out Aphex Twin at elegant soirées. The real connoisseurs, of course, nod knowingly and mutter that drukqs is “early period”.
Similarly, plainsong was seen as “classical” music for many centuries, and was also a largely rigid form, but there exist some absolute bangers in the canon, mostly unattributed because monks.
It’s hard to see the sweep of history from within it.
The last (well only) time I was in an opera house the retirees were listing to Blue Öyster Cult.
But there is an absolutely thriving collaboration- and improvisation-based music form grounded in jazz but open to novel & experimental instrumentation and ripe with influence from other contemporary forms like pop, hip hop, funk, reggaeton, metal. I'm thinking of people like thundercat, kamasi washington, nuclear power trio, tigran hamasyan, robert glasper, sungazer, domi & jd beck, louis cole etc.
If you like the sound of old school jazz, the standup bass the piano the brush drum shuffle, this stuff will be alien and hostile and won't feel like jazz to you. But if you like the musicianship of jazz, watching masters collaboratively invent new music in real time, this is where that ended up.