A Bangla band is any (modern) musical band that performs solely or mainly in the Bengali language and which uses Western principles of music.
As Western influences became more widespread, Bangla bands became popular with young people in the 1970s, both in India and Bangladesh, and have since become entrenched in modern Bengali culture.
However, recently traditional folk based bengali songs are getting significant polularity in Bangla band and such group is Mahul Folk Band of Kolkata, http://www.mahulfolk.com/.
Bangla bands use a wide variety of styles such as rock, pop, hard rock, heavy metal, grunge, folk, and fusion. Their music is influenced both by popular American music/Latin music/Caribbean music as well as traditional Bengali folk music such as Zaari, Saari, Bhatiali, Bhawaiya, Shyama Sangeet and Baul.