I want to know the answer to the following question:
Rebetiko was the base of what?
All the background I'm provided with is that "Rebetiko, initially a music associated with the lower classes, later (and especially after the population exchange between Greece and Turkey) reached greater general acceptance as the rough edges of its overt subcultural character were softened and polished, sometimes to the point of unrecognizability.". Is that enough to answer the question?