pitchblocks=klass()
function pitchblocks:init(width)
 assert_range(width,0,8,"width")
 self.width=width
 self.chunks={}
end

function pitchblocks:add(n,notes)
 assert(#notes==self.width)
 for i=1,n do
  add(self.chunks,notes)
 end
 return self
end