[3][4] In 1968 he played with Joachim Kühn and Aldo Romano in a band led by Barney Wilen at the Berlin Jazz Days.
During the 1970s he was a member of the Kurt Edelhagen Big Band (1972) and of Peter Herbolzheimer Rhythm Combination & Brass (Scenes (Live At Ronnie Scott's Club).
Chet Baker, Coleman Hawkins, Oliver Nelson and Benny Bailey engaged him for their concert tours and record productions, as well as German musicians such as Eugen Cicero, Horst Jankowski and Volker Kriegel.
In the mid-1970s, Lenz joined with the drummer Peter Giger in "Clarinet Contrast", an avantgarde band around the clarinetists Perry Robinson, Theo Jörgensmann, Bernd Konrad and Michel Pilz.
In the late 1970s he founded his combo Günter Lenz Springtime, an international jazz-fusion band with members as Bob Degen, Claus Stötter, Frank St. Peter, Johannes Faber, Leszek Zadlo and Joe Nay.