Klezmer (קלעזמער or כּלי־זמר) is an instrumental musical tradition of the Ashkenazi Jews of Central and Eastern Europe. The essential elements of the tradition include dance tunes, ritual melodies, and virtuosic improvisations played for listening; these would have been played at weddings and other social functions. The musical genre—also sometimes known by the earlier term freilach music (freilach, "joyous, happy")—incorporated elements of many other musical genres including Ottoman (especially Greek and Romanian) music, Baroque music, German and Slavic folk dances, and religious Jewish music. As the music arrived in the United States, it lost some of its traditional ritual elements and adopted elements of American big band and popular music. Among the European-born klezmers who popularized the genre in the United States in the 1910s and 1920s were Dave Tarras and Naftule Brandwein; they were followed by American-born musicians such as Max Epstein, Sid Beckerman and Ray Musiker.
After the destruction of Jewish life in Eastern Europe during the Holocaust, and a general fall in the popularity of klezmer music in the United States, the music began to be popularized again in the late 1970s in the so-called Klezmer Revival. During the 1980s and onwards, musicians experimented with traditional and experimental forms of the genre, releasing fusion albums combining the genre with jazz, punk, and other styles.
The term klezmer, as used in the Yiddish language, has a Hebrew etymology: klei, meaning "tools, utensils or instruments of" and zemer, "melody"; leading to k'lei zemer , meaning "musical instruments". This expression would have been familiar to literate Jews across the diaspora, not only Ashkenazi Jews in Eastern Europe. Over time the usage of "klezmer" in a Yiddish context evolved to describe musicians instead of their instruments, first in Bohemia in the second half of the sixteenth century and then in Poland, possibly as a response to the new status of the musicians who were at that time forming professional guilds.