As for the music itself, when did it really start? Hard to say but we can narrow it down by acknowledging that wherever whites and blacks in America came in close and constant contact, rocknroll resulted. This means that rocknroll didn’t arise from any one source but several concurrently as well as consecutively but independently. Consequently, the rise of minstrelsy in the 1840s was an early form of rocknroll and I think this is hard to deny. Elvis was decried by many whites in the 50s as a white man dancing and singing like a black man and in minstrelsy white men commonly donned blackface and played banjos while singing and dancing like black men (although women often got in on the act just as they did with rocknroll). Rocknroll was regarded as noise and minstrelsy was similarly regarded in its day. Indeed, in both styles, making noise was the very purpose, its raison d’etre.
Blackface minstrel with obligatory banjo which was to minstrelsy as the electric guitar is to rocknroll. Although images as this are now regarded as shamelessly racist and offensive, it was considered perfectly acceptable in the heyday of minstrelsy and no offense was intended. Whites couldn’t perform black folksongs as white people, so they became black which was seen as acceptable. We see things through different eyes today. The link below let’s you hear the type of music the above men would have performed. The man in the link, Felix “Sonny Boy” Wilson, is a modern minstrel performer and does not wear blackface because it is now socially unacceptable. In the 19th century, it would have been socially unacceptable for him to perform this way in public unless he blackened his face first. The custom became so ingrained that even black minstrels often wore blackface during performances.
Old Time Music in Galway Ireland - YouTube
From that to this:
Just a matter of degree, really.