function str = inst2str(instclass)
% str = inst2str(instclass)
% instclass can be son, nb, bb, os
% str is 'son', 'nb', 'bb', 'os'
% (there is probably a better way to do this)
if isa(instclass, 'son')
   str = 'son';
elseif isa(instclass, 'nb')
   str = 'nb';   
elseif isa(instclass, 'bb')
   str = 'bb';   
elseif isa(instclass, 'os')
   str = 'os';   
else
   fprintf('cannot deal with instrument class:\mn')
   instclass
   return
end