Complex sentence: Incidental music was not a feature of the main "Callan" series except "A Magnum for Schneider" where "Girl In The Dark" was repeatedly played in scenes where Callan got to work.
Split into simpler sentences: Incidental music was not a feature of the main "Callan" series. The exception was "A Magnum for Schneider" where "Girl In The Dark" was repeatedly (over) played in scenes where Callan got to work.