Stahnke studied composition with Wolfgang Fortner (1970–1973), with Klaus Huber and Brian Ferneyhough (1973–1974), and with György Ligeti (1974–1979).
[2] He also holds a doctoral degree in musicology, with a thesis on the subject of Pierre Boulez's Third Piano Sonata (1979, under Constantin Floros in Hamburg).
In 1979–80 he went to the United States to study with the microtonalist Ben Johnston in Urbana, Illinois, and with the computer music researcher and composer John Chowning at Stanford University, California.
Since 1989 he is professor of composition and music theory at the Hochschule für Musik und Theater Hamburg.
Since 1999 he is a member of the Freie Akademie der Künste Hamburg, where he was the director of the Section of Music until 2023.