These are not homeless people or rascals. They are part of the Orchestra of the Blind, and they play beautiful music around the streets of Sofia.
The orchestra was founded in 1922 by the Bulgarian Union of the Blind. At that time, it consisted of four violins, a cello, a flute, a clarinet, and a piano. They participated in numerous charitable concerts all over the country in order to raise funds for their organization.
Today, an additional function they have is to entertain the passers-by and, probably, to remind us that they are still there.