Daniel Kahn sings Leonard Cohen's 'Hallelujah' in Yiddish.

Yiddish is roughly 75% medieval German, 15% Hebrew and 10% of whatever is the common language of wherever a particular population of Jews is living. For instance, Lithuanian Yiddish is different from Ukrainian Yiddish or Bulgarian Yiddish or Hungarian Yiddish or American Yiddish etc.

Hebrew was the language of prayer equivalent to Church Latin for Catholics, so it was thought blasphemous or at least irreverent to speak of everyday matters in it.

Thus medieval German became the language of Germany's Jews in that period, same as everyone else living in that region. When the Polish rulers invited the Jews East in the 1500s to be the middle men between peasants and nobility they naturally took this language with them. Except for very rare occasions they did not intermarry with the Slavs, so kept speaking it among themselves down the generations. For those who remained 'home' in the various German principalities and kingdoms, German as a language simply evolved and they spoke that throughout its changes- Yiddish is solely a differently-pronounced Eastern European dialect for the isolated. ('A language is a dialect with an army and navy' -Max Weinreich)

It doesn't exist in the Mediterranean countries- the main linguistic component there is 75% medieval Spanish or Italian or Portuguese or Greek, etc. with the two other proportions about the same.

Anyway, here's the song.