Let me recommend playing with the score visible, the Piano Concerto #3 in D Minor, Op. 30, by Sergei Rachmaninoff. The work was composed in 1909, the same year as Mahler's Ninth Symphony, and likewise represents a culmination of post-romanticism going modern.
The performance is by Alexis Weisenberg on RCA Victor back in 1968, with the Chicago Symphony under George Pretre.
A high point of the work is the cadenza at the end of the Development section of the first movement. Weissenberg plays the version that starts “leggiero”, and builds up to the famous chordal climax. I think this is really the more difficult of the two. But I grew up with the Ossia, played by Van Cliburn with Konrashin in 1957 on RCA. .
The piano concerto, besides one of the most technically difficult in the literature, is remarkable in the way Rachmaninoff interrelates the themes from the three movements, finally justifying the “big tune” in D Major at the end, which has evolved from everything that came before. The opening starts with a very simple melody in common time that gradually gets more elaborate. Very quickly the theme comes to a pianistic climax on the dominant A Major, which could run the risk of sounding trite. The concerto constantly uses Rachmaninoff’s personally colored harmonies, layered on top of what sounds like folk song. The heavy use of accidentals and passing tones and progressive half-step modulations overlays what could otherwise be a hackneyed and obvious tonal scheme. The “Ossia” cadenza comes to another big climax on the dominant before its pronouncement in the original d minor.
The slow movement is said to start in F# Minor, but the music actually languishes in D minor and seems to be transitioning to the dominant A Major (relative to the first movement) before an extensive middle section in D-flat Major, resembling one of Rachmaninoff’s late preludes.
The Finale, Alla Breve, starts with a natural interplay between d minor, dominant a minor, than then secondarily relative C Major and minor. The famous “scherzando” middle section in E-flat has its own “middle of the middle” in E with a “prelude-like” slow section, based on previous materials, anticipating the big tune at the end.
When I watch the score I marvel at how Rachmaninoff (or any great composer) wrote down such a masterpiece entirely by hand. I wrote out my second Sonata by hand in my junior year in high school on a kitchen table on snow days – I’ve come back to this again soon on Wordpress. Given the pressure of today’s young composers to make a living on commissions and be clever, I wonder if any composers have the time to come up with a postromantic masterpiece on the scale of the Rachmaninoff Third. Yes, they can be clever. Have they lost interest in the tradition of romantic music turning modern, and blowing itself up with its grand scales? Or is it, even with modern software tools like Avid Sibelius, becoming an impossibility to pull off?
The Concerto gets a lot of attention in the 1996 film "Shine" and then the biography "Hello, I am David", both about pianist David Helfgott.
Update: Dec. 26
Here's some sheet music for the Ossia cadenza, starting at 10:00. Note the Rachmaninoff "gets away" with some repeating harmonies in a 3+1 pattern, or sometimes 2+2. Here's a source on which cadenza pianists perfer.