Swamp blues, sometimes the Excello sound, is a subgenre of blues music and a variation of Louisiana blues that developed around Baton Rouge in the 1950s and which reached a peak of popularity in the 1960s. It generally has a slow tempo and incorporates influences from other genres of music, particularly the regional styles of zydeco and Cajun music. Its most successful proponents included Slim Harpo and Lightnin' Slim, who enjoyed a number of national rhythm and blues hits and whose work was frequently covered by bands of the British Invasion.