He was professor at the Folkwang-Hochschule Essen, the Musikhochschule Köln, the Tokyo University of Fine Arts and Music and, for more than three decades, at the Hochschule für Musik Freiburg.
[2] At the same time, he became soloist, concertmaster and second conductor of the Staatsoper Hannover[2] and played Brahms's Violin Concerto with Franz Konwitschny,[3] who engaged him for further concerts with the Dresden Staatskapelle and the Leipzig Gewandhaus Orchestra.
As a conductor, he led a production of the operetta Ein Walzertraum by Oscar Straus, with the Viennese singer Gretl Schörg.
[3] Marschner gave master classes in Ankara, Beijing, London, St. Petersburg, Warsaw, Weimar, and in Łańcut Castle in Poland.
[7] Marschner became also director of the Pflüger Foundation which maintains a school for string players until age 16 with a focus on chamber music.
[8] Marschner's recording of Schoenberg's Violin Concerto with Michael Gielen and the SWR Sinfonieorchester Baden-Baden und Freiburg was critically acclaimed.
Marschner played world premieres such as Luigi Nono's Il Varianti in Palermo, violin concertos by Winfried Zillig with Hans Schmidt-Isserstedt in Hamburg, by Bernd Alois Zimmermann in Cologne, by Igor Stravinsky in Cairo, and other works.
As a premiere, Marschner performed the revised version of Karl Amadeus Hartmann's Concerto funebre in Braunschweig in 1959 with the local Staatstheaterkapelle conducted by Heinz Zeebe.
In performances with the Rostov-on-Don Philharmonic and the Voronezh Symphony Orchestra, also with the composer as conductor and the Russian violinist Olga Pogorelova, it was described as one of the best instrumental concerts of the twentieth century.
The high-ranking performances of his Second Violin Concerto with Rainer Kussmaul and the American violinist Oleg Kryssa in Weimar as well as his own interpretations found great resonance among Japanese experts, at the Kirishima Festival, in Tokyo and Osaka, among others.