These music genres are usually characterized by its instrumentation (accordion, zabumba (a snare drum variation), triangle, rebecha and so on). These genres usually portrait as a topic the harshing rural life in the region, characterized by its dry bioma.
Finally, there's also a very unique characteristic in these music genres: they are played on mixolydian scale. This characteristic is very particular and remarkable from the music at Northeastern Brazil, and it's not present in the music from the rest of the country.
How was mixolydian introduced in that particular region and why it's not as present in the rest of the country's folk music?
Quinteto Armorial - Do Romance ao Galope Nordestino (1974) :
Luiz Gonzaga - Asa Branca ft. Fagner, Sivuca, Guadalupe :
Cego Com Cego · José Miguel Wisnik · Tom Zé :