Ziehn (1845-1912) develops his theory of counterpoint. Key notions are: (i) inversion, in a 'real' rather than tonal, procedure, which often requires all twelve semitones and is not fixed to any particular key and (ii) canon - Ziehn saw imitation as a primary source of musical ideas. Ziehn was greatly influenced by Ferrucio Busoni, another sadly underappreciated composer and contrapuntalist, and it remains to be seen how much he may have influenced Schoenberg.