Here are the semi-great "S" composers who didn't fit into my original list of great composers or its immediate sequel. If I still left out someone who deserves mention, or if you want to know more about (for example) Sessions, Shapero, or Stanford, remember my three favorite letters: WTS!
Sarasate (Pablo de) was a Spanish-born, Romantic composer and violinist, or perhaps I should have put it the other way around. His music mainly showed off his virtuoso skills, and many of his pieces were elaborations or variations on themes by other composers. His Carmen Fantasy (based on themes by Bizet), Zigeunerweisen, and Navarra (featuring two violin soloists!) are among his best-known works. His Spanish-accented music inspired other composers to depict the spirit of Spain in their works.
Satie (Erik) was an experimental French composer around the turn of the 20th century. His most-celebrated works are a handful of short piano pieces, variously titled Gymnopédies, Gnossienes, and Ogives. His name is often mentioned in the same sentence as the word "precursor," e.g. when it is asserted that he influenced Debussy, Ravel, Schoenberg, etc. Frankly, I'm not inclined to give him that much credit, though in certain stumbling ways his music seemed prophetic of things to come.
Scarlatti (Domenico), the son of a Baroque opera composer (Alessandro), wrote operas and church music early in his career, but spent most of his life serving as a music teacher to the princesses of Portugal and Spain. He is now revered as a great composer of keyboard music, some written as exercises for his royal students, and much of it inspired by the folk music of those countries. His over 500 single-movement sonatas, mostly published after his death, are an exciting and monumental part of the classic keyboard repertoire.
Schickele (Peter) is both a composer and a humorist, famous for his facetious "discovery" of P.D.Q. Bach, and for hosting an educational program (Schickele Mix) that used to air on public radio. Some of his joke pieces have serious merit and are performed by small and large ensembles to this day (including the St. Louis Symphony Orchestra!) - and I think his Unbegun Symphony should be the final exam in many a college-level music appreciation course ("List as many titles as you can of the pieces quoted in this piece").
Schnittke (Alfred) was a Soviet-Russian composer who broke away from strict serialism to write what he called polystylism; that is, music blending the styles of different historical eras, as well as contemporary "popular" music. His works include 10 symphonies (numbered 0-9), 18 concertos, and the opera Historia von D. Johann Fausten, featuring a microphone-toting devil. Schnittke died several times, recovering each time except the last; isn't modern medicine wonderful? But now that he is quite dead, we can appreciate his very interesting grave marker (click it for a closer look).
Schoenberg (Arnold) was an Austrian-American composer who headlined the expressionist, atonal, and serialist movements in musical composition. Some of his earlier works are in a lush, late-Romantic style, such as Verklärte Nacht; later he experimented in extremely dissonant music that somehow combined emotionally intense psycho-dramas with intricate mathematical formulas worked out in music. He pioneered in using "twelve-tone rows" as the motivic basis of his music, and for a while during the mid-20th century, no composer was taken seriously unless he followed Schoenberg's example. Once you have heard some music of this style, you may understand why many composers rejoiced to leave it behind.
Schütz (Heinrich) is the 17th century composer regarded, by many native German speakers, as the all-time master of setting German words to music. Trained by Gabrieli of Venice, he put out a great deal of sacred music based on texts from Luther's Bible, many of them written for contrasting groups of voices and/or instruments answering each other from opposite sides of a church. His motets, written for various numbers of voices, were published in various collections with titles like Cantiones sacrae, Symphoniae Sacrae, Geistliche Chor-Musik, Psalmen Davids, and Schwanengesang ("Swan Song"-actually based on the Lamentations of Jeremiah). He also wrote two Passions and a Musikalische Exequien, the nearest the Lutheran Church could get to a Requiem. His best known motet is probably Saul, Saul, was verfolgst du mich (Saul, Saul, why do you persecute me). I would recommend any of his works - and once you start listening to some of them, you may end up getting hold of all of them. I particularly recommend the recordings of Geistliche Chor-Musik by Craig Smith and the Chorus of Emmanuel Music.
Schuman (William) was an American composer who was president first of the Juilliard School of Music, then of New York's Lincoln Center. Somehow he still found time to leave behind eight symphonies (numbered 3-10), a violin concerto, the American Festival Overture (I remember hearing the St. Louis Philharmonic play it once), the Mail-Order Madrigals (based on advertisements in an old Sears-Roebuck catalog), and best-known of all, the New England Tryptich. He also wrote ballets, operas, and songs from texts by Whitman, and orchestrated Charles Ives' organ Variations on "America" (the tune of "My country, 'tis of thee"). My interest in this Schuman has been growing lately!
Scriabin (Alexander) was a religious wacko who followed theosophy and apparently thought he was a Messiah. One gets that impression on hearing his thoroughly loathesome symphonies (mind you, "loathesome" is a musical term I reserve specially for them). He was also a hypochondriac who died from an infected shaving cut, a synesthete who associated musical pitch with color, an academic failure whose student composition exercises became required reading at the very conservatory that flunked him, and the father of a child prodigy (composer and pianist Julian) who tragically drowned at age 11. Also, the Molotov cocktail may have been named after his nephew. Honestly, with Scriabin there is no end of amazing factoids, but somehow I still can't get around mentioning his piano music, which included 10 very original and unusual sonatas, a concerto, numerous preludes and etudes, and other pieces, many of them based on a chord of his own invention. Let's just be thankful he never finished one piece that was supposed to bring about the end of the world.
Smetana (Bedřich) was a Czech composer who is best known for his opera The Bartered Bride and his cycle of symphonic poems Má vlast, which include the celebrated orchestral showpiece The Moldau. He also wrote an autobiography in the form of a string quartet (From My Life). He was an early leader in a 19th-century movement to incorporate national folk music into fine-art musical works. Unfortunately he lost his hearing, and eventually his mind, tormented by an auditory hallucination of a piercingly high musical note.
Spohr (Louis) was a German Romantic composer who wrote numerous works in every genre, including 9 symphonies, 16 violin concertos (of which the single-movement 8th is still played), 2 double-violin concertos, 4 clarinet concertos, 36 string quartets, 2 double quartets, and an opera that was banned by the Nazis because of its theme of interracial love. He was the first conductor to use a baton, and invented both the violin chin-rest and the idea of putting those helpful "rehearsal numbers" in a score. Most of his music went out of fashion after the Victorian era, but I'm told his autobiography is good reading.
Stenhammar (Wilhelm) was a Swedish pianist, conductor, and composer in the early 20th century. He is remembered for his Second Symphony, his two piano concertos, some Swedish cantatas, and six very important string quartets.
Sweelinck (Jan Pieterszoon) was a Dutch composer whose career bridged the Renaissance and Baroque periods. I have heard some of his beautiful vocal music (motets, specifically, though he wrote secular works as well). Nevertheless, his reputation mainly stands on his keyboard music, including some organ pieces I wouldn't like to be without.
Szymanowski (Karol) was an early-20th-century Polish pianist, composer, poet, and novelist (who would probably also be a registered sex offender if he lived today). Many of his literary works were dedicated to this guy, 'nuff said. As a composer he specialized in a strangely attractive style of music that sounds tonal but isn't. He wrote 4 symphonies, 2 violin concertos, 2 string quartets, and a Stabat Mater, plus operas, ballets, piano pieces (most notably his Études), etc. His music, influenced by Polish folk music, often has a quality of dreamy improvisation.