Semkow was born in Radomsko, Poland, later took French citizenship and resided in Paris.
His conducting mentors included Erich Kleiber, Bruno Walter, and Tullio Serafin.
He was an assistant conductor with Yevgeny Mravinsky with the Leningrad Philharmonic Orchestra.
[1] Semkow held posts as artistic director of the National Opera in Warsaw (1958-1959), principal conductor of the National Opera in Warsaw (1959–62), principal conductor of the Royal Danish Opera and the Royal Danish Orchestra in Copenhagen (1966–76), as well as music director of the Orchestra of Radio-Televisione Italiana (RAI) in Rome.
He was a regular guest conductor of the National Philharmonic in Warsaw and of the Detroit Symphony Orchestra over a 40-year period, including guest appearances over 24 consecutive seasons from 1986 to 2009.