 He has established a reputation as a concert and oratorio singer in the major musical centres of Europe, the USA and Japan, working with such conductors as Gary Bertini, Neville Marriner, Vittorio Negri, Zubin Mehta, and Nikolaus Harnoncourt, among others.He has performed in Austria, France, Japan, Netherlands, United Kingdom, and the United States and is well received by critics.Kowalski is still a member of the Comic Opera ensemble, and performs in the Volksbühne.