How much influence black music had on minstrel performance remains a debated topic. Minstrel music certainly contained some element of black culture, added onto a base of European tradition with distinct Irish and Scottish folk music influences. Musicologist Dale Cockrell argues that early minstrel music mixed both African and European traditions and that distinguishing black and white urban music during the 1830s is impossible. Insofar as the minstrels had authentic contact with black culture, it was via neighborhoods, taverns, theaters and waterfronts where blacks and whites could mingle freely. The inauthenticity of the music and the Irish and Scottish elements in it are explained by the fact that slaves were rarely allowed to play native African music and therefore had to adopt and adapt elements of European folk music. Compounding the problem is the difficulty in ascertaining how much minstrel music was written by black composers, as the custom at the time was to sell all rights to a song to publishers or other performers. Nevertheless, many troupes claimed to have carried out more serious "fieldwork". Just as the American people came from all over the world, some of the first forms of truly American music and drama were composed of elements from many different places.