As a bassist, Wielecki performs contemporary solo works across the Europe, in Azerbaijan, and the United States. He has been involved in the promotion of contemporary music and artistic education, leading programs on new music for children and youth at the Polish Radio. In 1992, Tadeusz Wielecki chaired the artistic committee of the World's Music Days of the International Society of Contemporary Music in Warsaw. His Concerto A Rebours for violin and orchestra was listed among the recommended works at UNESCO's International Composers' Tribune (1999) in Paris.
He is also a member of free-improv band Laterna, well known for their works on OBUH Records.