The difficulty with answering this question is that it conflates a whole host of different traditions together, many of which did not have much of anything to do with one another. Classical music evolved, first, primarily through the religious practices of European Christians (starting ca. 9th century AD), and then moving to a largely secular zone of courtly theater and entertainment around 1600, before dipping slightly into upper Bourgiouse territory around 1800, where it has largely remained to this day. Classical music didnt really evolve into "the music we have now," unless by "the music we have now," you mean, like, this. Classical music has pretty much always been music for white Christian elites.

If by "the music we have now," you mean, like, popular music, then the roots are numerous and lay largely outside the classical realm. /u/hillsonghoods can (and probably already has elsewhere) provide more detail about this history, but the cliffs notes version is that it came from a mixture of musical practices developed by former slaves in the US, anglo saxon balladry, social dancing, musical theater, and so on. Only the last of these - the "great american songbook" as developed through decades of Broadway and movie musicals - has any semblance of a connection to the classical tradition (by way of operetta).

So I think you gotta narrow your scope if you want an answer that meets the standards of /r/AskHistorians. As it stands, it's too broad to answer in any adequate fashion. What exactly is "the music we have today?" Should we assume that it all comes from a single tradition? Might there be a whole mess of traditions involved? Would it be possible to maybe isolate one strand of musical development you find particularly interesting, and ask us about the history of that strand?

I just thought from classical you got hymns, from hymns you got the old negro spirituals and from that dopwop to rock, soul and blues and those 3 you have everything you see today.

Now I haven’t researched any of this, just curiously looking back on lots of my fav music. (I guess that’s sort of research right?)

But thank you for the early part of classical info... I never knew that.

Thanks for the insight!