Klezmer music is the traditional music of Ashkenazi Jews, or Jews of Eastern European descent. Although the music was born in Eastern Europe, its roots can be traced back to the folk music, troubadour songs and church music of Central and Western Europe. Music was one of the few professions (along with money lending and trade) that Jews were allowed to practice in Medieval Europe, so in most large towns and cities, professional bands of Jewish musicians formed. As early as the 14th century, European Jews began migrating east, fleeing persecution and inquisition in an increasingly intolerant continent, and bringing their music with them.
Throughout history, weddings have been among the most important ceremonies in Jewish culture. From Biblical times through the modern era, Jews have faced persecution, inquisition and other hardships, and weddings provided an opportunity to celebrate life and love, and everyone was invited. Consequently, the majority of klezmer is dance music, with specific dances corresponding to different types of songs in the klezmer repertoire. But klezmer isn't merely up-tempo, feel-good dance music; it can also include slower melodies that aren't intended for dance.
Klezmer has always been heavily influenced by other styles of traditional and popular music, giving it room to grow. The instruments have changed with the times, as have the melodies. In the 18th and 19th centuries, klezmorim were traveling musicians who would swap and learn songs from other non-Jewish musicians, ultimately resulting in the highly eclectic sound that we now identify as klezmer. Over the past half century, klezmer has experienced a revival in the United States and elsewhere, as American Jews have become interested in their cultural heritage. Because of that revival, klezmer survives today, and continues to be one of the most interesting types of folk music in the world.