What is the difference between the Romantic and post-romantic periods?

Question

This question came about when I was reading Blair Allen Johnston’s dissertation, ‘Harmony and Climax in the late works of Sergei Rachmanioff’

He loosely groups the post romantic period within 1890-1940 and acknowledges the possible counterproductiveness of period groupings.

I quote: “Romantic is characterized by chromatic expansion and the development of striking elaborations of linear tonal syntax, then the Postromantic is characterized by exaggeration and ultimately fragmentation of tonal syntax, and the juxtaposition or superimposition of conventional functional tonal structures and intense chromatic and/or modal structures that challenge and even deform the functional tonal basis. In my view, complex interaction of variegated melodic-harmonic components is one source of the continuing fascination Postromantic music holds.”

https://deepblue.lib.umich.edu/handle/2027.42/63739

I understand this quote does answer the question that I'm asking. But I'm hoping for a clearer explanation as I don't fully understand what he's saying, in terms of chromatic expansion, elaborations of linear tonal syntax, exaggeration and fragmentation of tonal syntax and the superimposition of conventional functional tonal structures and intense chromatic and modal structures.

Answer 1

The Main Characteristics of Romantic Music

https://www.rpfuller.com/gcse/music/romantic.html

• Freedom of form and design. It was more personal and emotional.

• Song-like melodies (lyrical), as well as many chromatic harmonies and discords.

• Dramatic contrasts of dynamics and pitch.

• Big orchestras, due mainly to brass and the invention of the valve.

• Wide variety of pieces (i.e. songs up to five hour Wagner operas)

• Programme music (music that tells a story)

• Shape was brought to work through the use of recurring themes.

• Great technical virtuosity.

• Nationalism (a reaction against German influence)

  Postromantic (Blair Allen Johnston - the dissertation of your link)

• Deformation and Structural Tension

• Hyperdissonance: Definition and Initial Analytic Applications

• Formalizing the Model: Tension Arcs

• Exaggeration of Tonal Premises

• Distortion of Tonal Premises

• A Parenthesis: Neutralization of Tonal Premises

I don't fully understand what he's saying, in terms of chromatic expansion, elaborations of linear tonal syntax, exaggeration and fragmentation of tonal syntax and the superimposition of conventional functional tonal structures and intense chromatic and modal structures.

Let's assume that if someone will be able to find and read this dissertation he will know or understand what is meant by chromatic extension.*1)

So let's pick another example...

Blair quotes:

However, the Encyclopædia Britannica provides a starting point: [A] musical style typical of the last decades of the 19th century and first decades of the 20th century and characterized by exaggeration of certain elements of the musical Romanticism of the 19th century. Postromanticism exhibits extreme largeness of scope and design, a mixture of various musical forms (e.g., opera and symphony), and heightened contrapuntal complexity (i.e., a long or vast array, or both, of simultaneous but independent musical lines or events). Often Postromanticism also embraces vivid religious or mystical fervour, a sense of longing, and a sense of the grim and the grotesque.

Exaggeration and fragmentation of tonal syntax

“Exaggeration” and “vast array…of simultaneous but independent musical lines or events” are particularly telling. From them, I offer a more specific observation: if the Romantic is characterized by chromatic expansion and the development of striking elaborations of linear tonal syntax, then the Postromantic is characterized by exaggeration and ultimately fragmentation of tonal syntax, and the juxtaposition or superimposition of conventional functional tonal structures and intense chromatic and/or modal structures that challenge and even deform the functional tonal basis. In my view, complex interaction of variegated melodic-harmonic components is one source of the continuing fascination Postromantic music holds. A basic claim in the present document is that Rachmaninoff was a Postromantic composer, not an anachronistic Romantic composer.

*1)

To describe the development of harmony from basic chords to diminished seventh chords, mediant, neapolitan 6th, Italian-, French- and German-Sixth until the Tristan chord would be a theme too vast to answer the chromatic extensions. The best advice would be to listen to the music of Rachmaninoff and analyze his chords and progressions. (Just the intro of his Piano concerto will provide us a full range of interesting harmony!)

Answer 2

Let me try to unpack the quotation a bit.

Romantic characteristics:

• "Chromatic expansion": more possibilities for use of chromaticism, in context, I think this refers mostly to harmonic patterns (like chromatic chord progressions you wouldn't generally find in Bach or Mozart, for example)
• "Development of striking elaborations of linear tonal syntax": "linear tonal syntax" here is likely a reference to Schenkerian theory, one of whose focuses is on trying to isolate so-called underlying "linear" voice-leading structures (e.g., simple descending lines) that are supposedly elaborated with lots of other "surface-level" notes, in a manner similar to baroque-style diminution and embellishment

The "striking elaborations" he's referring to are probably places where these "linear" structures become quite chromatic and/or incorporate extensive chromatic digressions in romantic period music.

Postromantic characteristics:

• "Exaggeration and ultimately fragmentation of tonal syntax": in other words, traditional tonal progressions get used in both exaggerated ways (e.g., lots of repetitive tonal progressions) and fragmented (e.g., rather than getting full phrases of tonal harmonic progressions, you merely get fragments -- small parts of chord progressions that sound sort of like what Mozart would do, but then deviate off in an unexpected manner or get interrupted by other harmonies)
• "Juxtaposition or superimposition of conventional functional tonal structures and intense chromatic and/or modal structures": this could be a reference to a lot of things, but generally it's referencing the idea that you might have something that sounds simple and harmonically straightforward (similar to Mozart) and then suddenly an intense chromatic passage follows or inserts itself, or rather than following "tonal" progressions, the music veers off into a mode "modal" harmony
• "Challenge and even deform the functional tonal basis": in other words, at some points you may not know where the harmony is leading anymore, you may not end up in the key you expect; in general, the harmony becomes unpredictable compared to what you'd expect in Mozart
• "Complex interaction of variegated melodic-harmonic components": more varied harmony (as noted in the points above), combined with melodic/contrapuntal driving forces that are also more varied than the typical Schenkerian reductive patterns that are often used to analyze romantic period music

(I use "Mozart" above as just an example of traditional "tonal" music that usually has very clearly defined functional harmony, with very predictable progressions and phrases, etc.)