^ Me too. But a week or so back someone here "corrected" me. Personally, I don't think it makes sense to call Mahler post-romantic when his music is surely "high romanticism" or "late romantic". To me post-romantic should mean not romantic but coming after romanticism. It seems like a good catch all phrase for what used to be called modernism (1920 - 1950) but is now quite old! Of course, this would mean that within the post-romantic there are both neoclassical and neo-romantic works and composers, but I don't see that as a problem.

Mind you, I don't find these categorisations easy, anyway. Most people are fine with considering Beethoven as a classical composer but I feel he was an early Romantic from his middle period onwards. It doesn't make sense to me to think of the Eroica or the Harp as classical works. But ultimately these terms are to assist us in communicating so I guess we need to use the terminology in the way required.

 

I think the discipline of history of music is too preoccupied with trying to make homogenous political parties out of art, with any sort of dissent or outliers being considered "problematic", or called names.

I consider the concept of "style" being equalled to "period" as fallacious.

The way it should be seen is that genres start and go on indefinitely. What can be said is that they have more or less practitioners at a given point, but the style is still present---composed by at least one composer, performed by at least one musician, or read by at least one non-historian.

Renaissance: 1400-
Baroque:1600-
Classical:1750-
Romantic: 1800-
Modernist: 1900-
etc.

 

I thought this was a good blurb on the distinction between late- and post- Romanticism. I always felt Strauss and Mahler were more modern sounding than the likes of Tchaikovsky, Brahms. Debussy is also sometimes is called a post- Romantic. I think it was Stravinsky who called him the first modernist. I've also heard Prokofiev's 6th sonata as the first expression of modernism.

https://www.classicalarchives.com/period/7.html

 

My personal categorization of major figures:

Puccini, Strauss: Late Romantic
Mahler: Transition figure between Romanticism and Modernism
Rachmaninoff, Elgar: Neo-Romantic
Vaughan Williams, Sibelius: Post-Romantic

 

I wish it was an easy thing to categorize, since I'm teaching it to high-school music students. I recently took a 3-month subscription to oxfordmusiconline, but it isn't a term discussed much, you have to look for it in different articles. All the composers you mention could be postromantic...Neo-romantic is something I connect with postmodernism.