Hartmann was a student of Holger Byrding, studied at the conservatory and at the Opera School in Copenhagen from 1957 to 1962.
He made his debut at the Opera House in Copenhagen in 1962 as Rodolfo. He stayed there until 1967. He continued to sing in Copenhagen
as a guest.
From 1966 to 1972, he sang in Hamburg. His further guest appearances were in: Bayreuth (1965-66 as Walther von der
Théâtre de la Monnaie Bruxelles: Fidelio as Jacquino on October 30-November
2/4/6 1965, with Ernst Kozub (October 30-November 2/6)/Niels Möller (November 11), Anja Silja,
Theo Adam (October 30)/Eduard Wollitz (November 2/4/6), Gustav Neidlinger, Gerd Nienstedt, Rita Bartos (October 30-November 2)
/Ghislaine Morèze (November 4/6), John Geentjens, Manfred Dorner, André Vandernoot);
Staatsoper Wien: Arabella
on February 24, 1970 as Matteo with Kurt Böhme, Christel Goltz, Lisa Della Casa, Olivera Miljakovic, Eberhard Waechter, Fritz Uhl, Hans Christian,
Herbert Lackner, Mimi Coertse, Elisabeth Höngen, Berislav Klobučar); Stockholm,
In Hamburg, he took part in the world premieres of Hamlet by R. Searle (1968 as Laertes) and Belagerungszustand by M. Kelemen
His repertory included Pylades, Tamino, Florestan, Froh, Steuermann, Narraboth, Matteo, Jim Mahonney,
Ismaele, Cassio, Vogelsang, Des Grieux (Manon Lescaut), Pinkerton, Luigi, Cavaradossi, Stewa, Lenski,
Dimitri, Jonathan (Saul og David), Leander (Maskarade), Alfred, ...
In 1970, he got so sick that it hampered his career that he gave up in 1972.
He recorded for Vox, Polydor, Unicorn (complete recording of Saul og David in 1978), and Danacord
(live and studio recordings 1963–66 - DACOCD623-24).
His performance as Cavaradossi with Lone Koppel and Ib Hansen was recorded in 1964 for TV.
Reference: Kutsch & Riemens