He subsequently conducted around thirty works of the repertoire such as Aida, Turandot, Porgy and Bess and West Side Story and also conducted his own rehearsals at the opera house, among others La traviata, Die Fledermaus, La pietra del paragone by Gioachino Rossini.
From 1978 to 2007, Seiffarth was music director and Chief conductor at the Musikalische Komödie in Leipzig.
[3] Numerous guest conducting engagements have taken him beyond Leipzig, to the Semperoper, the Berlin State Opera, the Metropol Theatre Berlin, the Staatstheater am Gärtnerplatz, and at the Staatsoperette Dresden [de] and at the Staatsschauspiel Dresden.
Seiffarth conducted numerous opera and operetta galas with international stars, was for several years the conductor of the annual benefit gala with José Carreras for the José Carreras Leukaemia Foundation and is a holder of the Kunstpreis der Stadt Leipzig.
He has rendered special services to the cultivation of the stage works of Robert Stolz and Franz Lehár as well as outstanding services to young musicians by directing the Young Conductors Operetta Workshop.