The practice in the German Protestant Reformation of setting sacred texts to the tunes of secular songs. An example is "Innsbruck, ich muss dich lassen" by Heinrich Issac, which became the Lenten hymn "O Welt, ich muss dich lassen". (This tune is known to American Lutherans as "Now rest beneath night's shadow" or "Oh, bread of life from heaven".) Popularized by Martin Luther, who quipped "why should the Devil have all the good tunes?". Some musicologists have speculated that Luther's famous hymn tune "Ein' feste Burg" is based on a drinking song.