Your favorite 5 works by your favorite 20th C. tonal composer

[Chaszz]

Richard Strauss
Four Last Songs
Der Rosenkavalier
Don Juan
Ariadne Auf Naxos
An Alpine Symphony

(And a word for three great lesser knowns -   Hubert Parry, Franz Schmidt, Franz Schreker)

[Brian]

I'm gonna deliberately get the format completely wrong. 

Five composers five each!
Shostakovich: Sixth, Ninth and Tenth Symphonies, Piano Quintet, Piano Concerto No 2
Atterberg: Third, Fourth, Sixth, and Eighth Symphonies, Violin Concerto
Gershwin: Rhapsody in Blue, Piano Concerto, Porgy and Bess, American in Paris, Three Preludes
Sibelius: Third, Fifth, Sixth and Seventh Symphonies, Swan of Tuonela
Roussel: Suite in F, Third and Fourth Symphonies, Bacchus et Ariane, Resurrection

Five composers one each!
Janacek Glagolitic Mass, Rachmaninov Preludes, Glass Symphony No 3, Kapustin string quartet, Hartmann Symphony No 6 oh wait he's atonal and I can't break all the rules  ... Bernstein West Side Story.

EDIT: Crap! I forgot Strauss' Metamorphosen. And Dorman's Piano Concerto. Let's stretch this to another group of five ... Gorecki Symphony No 3, Bax Tintagel, Moeran Sinfonietta. Blam-o!

EDIT II: And in the Soviets Who Aren't Shostakovich category: Weinberg Cello Concerto, Weinberg Cello Fantasia, Prokofiev Alexander Nevsky Cantata, Prokofiev String Quartet No 2, Khachaturian Gayaneh

[Florestan]

Rachmaninoff: PC 1-3, Symph #2, Three Symphonic Dances

[vandermolen]

Vaughan Williams:

Symphony No 6 and 9, The Pilgrim's Progress, 5 Variants on Dives and Lazarus, Sancta Civitas.

[Bulldog]

Shostakovich:

Op. 87 Preludes and Fugues
Op. 34 Preludes
Syms. - 4, 7 and 10

[Sergeant Rock]

Mahler Symphonies 4, 5, 6, 7 and 10 (not the Ninth, not DLvdE? No, the Tenth)

Sarge

[Lethevich]

Vaughan Williams - Violin Sonata, Symphony No.6 & 8, Flos Campi, Dives & Lazarus