During its 300 year history, the piano has proven to be the medium of choice for composers and virtuosi alike, providing a platform from which the greatest musical minds could show their genius. In chronological order, here is a woefully inadequate list of great pianists and composers who have so enriched the world of music.
The quintessential child prodigy, Mozart's genius flared rapidly, and was extinguished quickly. Though only 35 at the time of his death, Mozart's catalogue comprises over 600 works. Of these, we know of 25 piano concertos, 17 piano sonatas, and a host of other shorter, though no less consequential, piano works. Mozart's broader compositional style is notable for its beauty and simplicity, even though some of his works--like the unfinished Requiem--are far darker and more complex.
It is difficult to say with any certainty what Beethoven's greatest musical contribution was. Some may say his symphonies define the genre, and created a standard never quite matched by subsequent symphonists. Others might say his string quartets, especially his final six, were representative of Beethoven's vision, and therefore were the pinnacle of his compositional output. Still others argue that his piano works are his greatest, as evidenced by the fact that he never stopped writing them: 5 concertos, 32 sonatas, and dozens of other single-movement or smaller-scale works.
Every one of Chopin's numerous compositions involves the piano. Known during his lifetime as an astounding piano virtuoso, Chopin was in high demand as both a performer and teacher.
Despite spending half of his life in France, Chopin was a deeply nationalistic Pole, a fact that is heavily celebrated in Poland to this day. Chopin proved exceptional at blending Polish folk influences with the styles of established German composers, like Bach and Mozart. Pianists everywhere consider his sonatas, études, ballades, nocturnes, and many others, as favorites.
While Franz Liszt and Frédéric Chopin were considered friends throughout Chopin's unfortunately short life, the pair could not have been more different. While Chopin preferred intimate concerts and the patronage of a select few wealthy benefactors, Liszt enjoyed wide popular appeal, and was considered the preeminent piano virtuoso of the 19th century--possibly of all time.
Liszt's greatest contributions were in the development of musical forms, most notably the symphonic poem, influencing later composers like Richard Wagner and Richard Strauss. Sadly, Liszt's virtuosity is lost to history, as recording devices were not available until a few short years after his death.
Brahms was crippled by perfectionism, and it is due to this that we have his Piano Concerto No. 1 in D minor. Originally intended as his first symphony, Brahms felt he would be unfavorably compared to past symphonists, and that left him with a nearly fifty minute concerto. Pared down to three movements from the standard symphonic four movements, the premiere of Brahms' first piano concerto, with Brahms playing, received mixed reviews; though, contemporary appreciation for this work has only increased.
Brahms' further self-criticism pushed back his symphonic debut, finally premiering his Symphony No. 1 in C minor in 1876, a full 21 years after the appearance of its first sketches. Ever self-deprecating, Brahms is considered one of the three B's of classical music, enjoying the company of Bach and Beethoven.
Debussy's style is easily distinguished from that of classical composers. Distinctly French, he made use of nonfunctional harmony and unorthodox scales to create palettes of sound previously unheard. His unique use of unconventional ensembles and instrumentation shifted focus from form to timbre, allowing for experimentation in different sound colors.
For the piano, Debussy created lush harmonies that depend on the addition of sevenths and ninths, greatly expanding tertian harmony in the process.
Rachmaninoff's skill was formidable, as a composer, performer, and conductor. Frequently performing the premieres of his own compositions permitted him to make use of his gigantic hand span. This allowed him access to harmonies and power entirely unavailable to other pianists. As a result, his works assume a grand scope, both harmonically and formally.
Rachmaninoff's output remained a perfect example of Russian Romanticism to the end, with his most widely lauded piano composition Rhapsody on a Theme of Paganini being composed in 1934.
Avant-garde composer John Cage is a polarizing figure. Though he is not considered a virtuoso, his contributions to contemporary music are undeniable, especially with regard to the piano. His collection of short piano pieces, Sonatas and Interludes, calls for the use of prepared piano. By altering the piano's strings with nuts and bolts, Cage was able to create a wide range of sounds, comparable to a percussion section.
Until this point, whether a performer played Bach or Debussy, the piano's sound remained largely unchanged. The prepared piano of John Cage was revolutionary. Read about the longest performance piece currently being attempted, Cage's Organ²/ASLSP (As SLow aS Possible).