Robbie commented:
>[ I'm still confused: I thought that the principal melody voice on the
>[ Dutch Street Organ is the de-tuned double-Bourdon a la' Carl Frei.
>[ ... Someday we'll get it all sorted out !  -- Robbie

My understanding is that most street organs from the smallest (56 key) to
the largest (90 key and above) use at least two registers in the melody:
violins and bourdons.  These can be turned on and off independently and
played together to get a forte effect.  

The larger organs have even more registers with the 90 key organs having
5 or 6 registers in the melody and often replicating some dance organ
registers.  A similar arrangement is common with German fair organs as
well.  Ruth, for example, even in the model 36 (78 keyless) offered an
optional ocarina rank which allowed the melody to be played in violins or
the ocarina.  This register consisted of a rank of open flues and a rank
of stopped flues.  The musical effect was similar to the Dutch street
organs where the melody could be alternated between the sweet sound of
the violins and the more rounded tones of the bourdons.  

I think maybe your confusion comes with the fact that the bourdons is a
unique and prominently used characteristic for one voice of a Dutch
street organ but it is by no means the only voice they have.

I hope this helps.

Bob Conant