I can't address the "paragraph 51" aspect of this query (I found
nothing about it in McGilligan's recent Lang biography), but *M*
assiduously avoids any type of voice-over narration (although perhaps I
don't quite understand your usage of "narrator" here).  All sound is
diegetic, although near the film's beginning I believe it is the police
commissioner (Adolph Loos?) whose telephone conversation with a government
minister, perturbed over the police's lack of success in finding the
murderer, describes the police procedures that Lang portrays onscreen, in
a manner "narrating"  what is viewed.  Lang's most radical sound
innovation is beginning the film (after opening credits) with a completely
black screen, with the children's song about the "little man in black" on
the soundtrack, effectively prefiguring both the plot and the Lorre
character; eventually (as I recall), the black dissolves into a high-angle
shot of the children playing.  They undoubtedly exist, but I cannot think
of an earlier film that uses so effectively the absence of an image in
complete deference to the soundtrack, especially so at the film's
beginning, when the audience expects to "see" something.
_______________________________________________________________________________
                          William Lafferty, PhD

Department of Theatre Arts                           [log in to unmask]
Wright State University                           office (937) 775-4581 or 3072
Dayton, OH  45435-0001  USA                            facsimile (937) 775-3787

        The universe was once conceived almost as a vast preserve, landscaped
  for heroes, plotted to provide them the appropriate adventures.   The rules
  were known and respected, the adversaries honorable, the oracles articulate
  and precise as the directives of a six-lane parkway.  Errors of weakness or
  vanity  led,  with  measured  momentum,  to  the  tragedy  which   resolved
  everything.  Today, the rules are ambiguous, the adversary is  concealed in
  aliases, the oracles broadcast a babble of contradictions.

                                 --- Maya Deren, from her notes for *At Land*

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