These refrains would have been sung by the dancers in time with the dance.[16] In the 18th century, ballad operas developed as a form of English stage entertainment, partly in opposition to the Italian domination of the London operatic scene.[17] In America a distinction is drawn between ballads that are versions of European, particularly British and Irish songs, and 'Native American ballads', developed without reference to earlier songs. A further development was the evolution of the blues ballad, which mixed the genre with Afro-American music.[18]