O.S.T.R.

Adam Andrzej Ostrowski (, born 15 May 1980 in Łódź, Poland), better known as O.S.T.R., is a Polish rapper, musician, audio engineer and record producer, famous for his freestyle rap skills, ambitious lyrics and unique beats. He graduated from the Academy of Music in Łódź, violin class. He is one of the few Polish rappers who have received professional musical education. 
He has collaborated with American rappers such as Evidence, El Da Sensei, Craig G, Keith Murray, Jeru The Damaja, Lil' Dap, Sadat X and Canadian producer Marco Polo.
He has also collaborated with many Polish artists, including jazz musicians Michał Urbaniak, Hades, SOFA, Fokus, DJ Deszczu Strugi, DonGURALesko, Vienio i Pelson, Fu, Pezet, Sistars and Slums Attack. He is a member of bands such as Tabasko, Skill Mega, Killing Skills, Beat Brothers and musical project POE. He is also a former member of Obóz TA and LWC. In 2013, he shared the position of art director of Męskie Granie festival with alternative rock vocalist Kasia Nosowska.