Rimsky-Korsakov sounds more oriental, spanish, fairy tale.

Rachmaninov sounds more romantic, serious, sweeping, energetic, brutal, sometimes near-impressionism (slow changing textures).

Only Rachmaninov has a capella, piano. (Rachmaninov, Rimsky-Korsakov)

Simple island.

Schubert sounds more light, classical, repeating, closer to Mozart.

Rachmaninov sounds more russian melodic, sweeping, energetic, piano technical.

Only Schubert has string quartet, piano trio, german songs, piano quintet.

Only Rachmaninov has violin vocalise, liturgy. (Rachmaninov, Schubert)

Compare two most known late romantic russian composers.

Tchaikovsky sounds more dance, light, percussive.

Rachmaninov sounds more serious, brutal, sweeping.

Only Tchaikovsky has piano+violin+cello in this game.

Only Rachmaninov has religious chorus. (Rachmaninov, Tchaikovsky)

This is an interesting comparison of two romantic piano composers.

Chopin generally sounds more uniform, regular, repetitive. Other pieces sound very simple romantic.

Rachmaninov sounds more brutal, flexible, sweeping. Also he uses some russian melodies.

Chopin has only solo piano and piano concerto here. (Chopin, Rachmaninov)

This is a nice starting island. But some of composers will be harder to guess. (JS Bach, Beethoven, Chopin, Debussy, Glass, Mozart, Pérotin, Rachmaninov, Tchaikovsky, Vivaldi, Wagner...)

Two post-romantic russian composers here.

Scriabin is more abstract, cosmic, less tonal.

Rachmaninov is more melodic, simple, clear.

Only Rachmaninov has vocal works here.

Scriabin has only solo piano works and a Mysterium in this game. Mysterium is more dissonant and chaotic than Rachmaninov works. (Rachmaninov, Scriabin)

This is an interesting island with three composers of different periods.

Debussy is french impressionist with hazy mistical sound.

Rachmaninov is russian post-romantic with simple light melodies, piano bell chords and fast piano textures.

Shostakovich is russian modern with tragic, dissonant, abrupt, fugue, dark sound. (Debussy, Rachmaninov, Shostakovich)

Aside from piano and opera, which go immediately to Rachmaninov, this island seems to me very tough to play on. Symphonic styles of both composers are very close. I think, Bruckner sounds a bit more atonal or dissonating, while Rachmaninov tends to use more lyrical and simple melodies. (Bruckner, Rachmaninov)

Rachmaninov is post-romantic and beautiful. Gershwin is jazzy. (Gershwin, Rachmaninov)