That end date is a little late imo – of course there is always debate on this. Beethoven is dead in 1827, yet he is the quintessential Romantic composer, though his early work is considered Classical. Your timeline places him squarely in the Classical era.
In our competition, Beethoven selections are considered “classical.” We base it on the time that the composers lived, not on the style of their pieces. I believe that this is the generally-accepted convention when classifying music.
There are composers who are currently composing music that sounds “classical,” but it is not generally considered correct to call this music “Classical.” It is considered “Contemporary” because the composers live in the 21st Century.
I think that if someone wants to make a case for classifying music according to the style of music rather than the time period of the composer, they would have to make that very clear, or it could be confusing to most musicians and teachers who are used to the convention of using time periods.
In our competition, I believe that our rules make it clear that we are using time periods, not styles. Every once in a while, we’ll receive an application from a teacher who tries to make a case for Gershwin or Joplin writing classical music, but the “experts” that I consult always shoot this down.
Yet you offer none who do. I think Joshua wants music, not a lecture.
I have already expressed contrition about sounding like a snob. I apologize again for sounding like an “academic” and appearing “flustered” over terms.
But the fact is, if the OP wishes for a certain kind of music, it would be good if he follows the generally-accepted convention of musical periods by date. He is more likely to get responses from musically-knowledgeable people.
Just because a music store divides itself up into sections doesn’t mean that those sections are the Final Word when it comes to music literature and history. To musicians, “Classical” music means something different than it does to retailers.
BTW, I don’t consider myself an expert in musical periods. I rely on experts to help me determine whether the competitors’ pieces are in the correct period for our music competition. I call our local symphony conductor, or contact my university.
So I would suggest that the OP contact a university music department and speak with a professor who is an expert on music literature and history. They will be happy to help.