Lived 1882-1967. His name is pronounced "koh-DAI" (forgive my lack of proper pronunciation marks)
A 20th century composer, in the era of modernism. He was born and lived primarily in Hungary. A very good friend of fellow composer Bela Bartok, who went on to greater fame. Both Kodály and Bartok were very interested in Hungarian folk music. Together they extensively documented Hungarian folk music, which at the time was largely unknown.
Bartok was in many ways responsible for Kodály's fame. He recommended Kodály to many famous critics, and made Kodály a respected name in the musical community. He also defended Kodály from charges that his work was attempted imitation of the more well-known Bartok. In fact, the reverse statement would be just as true; both composers studied together and influenced each other.
Kodály added significantly to the Cello literature. His many cello works include his Sonata for Solo Cello, op.8, an incredibly complex and difficult cello piece. Before its publication, no truly innovative solo cello music had been written since Bach's 6 Suites for Unaccompanied Cello. Kodály's sonata is a true gem for any cello appreciator, as well as any virtuoso looking for a challenge.
In addition, Kodály is known for his Háry János opera, which became the most popular Hungarian opera.
Kodály's musical style is notably influenced by the folk music he extensively studied. Unlike many of the composers that succeeded him, he strove to create melody and harmony in his music despite its distinctively modern feel (lots of modern music, in a movement pioneered by Arnold Schoenberg, has ditched the traditional notions of harmony, melody and even musical connectedness {but of course, I'm totally biased}*).
Off the page, Kodály is famous (though less so) for promoting music education in schools. He believed in "Music for Everyone." A highly educated, knowledgeable scholar, as well as an incredible composer, Kodály deserves to be listened to more.
* As I said, I am biased against Schoenberg. A fellow noder has clarified this issue for me: "If it's unarguable that Schoenberg 'ditched traditional notions' of melody (etc.), then it's unarguable. But I think Schoenberg retained quite a traditional notion of melody, and even of continuity (connectedness). E.g. the Violin Concerto. It's just that they are difficult to hear because of the different harmonies. Sch. himself, while preening himself on destroying tonality, placed great emphasis on melody and structure. (Which was ignored by some of his imitators...)."
So, I hope that clears things up. Although I think it still stands that the movement that Schoenberg started eventually separated almost entirely with traditional harmony, continuity, melody and structure. In any case, my reason for bringing this up at all was simply to distinguish Kodaly from the "other" modernists, i.e. those associated with Schoenberg.
Sources:
The Essential Canon of Classical Music, by David Dubal, North Point Press, 2003
A Guide to Kodály, by János Breuer, Corvina Books, 1990
The Organization of American Kodály Educators, @ www.oake.org