I was recently referred to a very interesting article on lead
corrosion which could hold a few answers to lead corrosion in
instruments (piano key leads) or music boxes:

  Lead Corrosion in Exhibition Ship Models
  http://www.navsea.navy.mil/nswc/carderock/pub/cnsm/lead/lead_01.aspx 

It appears that the presence of wood and varnish, especially in absence
of air exchange, promotes lead corrosion.  Wow!

Jurgen Goering

 [ At http://www.navsea.navy.mil/nswc/carderock/pub/cnsm/lead/lead_02.aspx 
 [ "Acetic acid acts upon lead and transforms it into lead carbonate
 [ which is the white, granular, powder we frequently see on lead ship
 [ model fittings."  -- Robbie