Getting blobs from similar colored contours in grayscale image

edit

I want to select the staff lines as individual blobs in either of these images:

http://i.stack.imgur.com/7LJ25.png

http://i.stack.imgur.com/V95Le.png

The staff lines have similar darker gray color than the rest of the image.

Is this possible?

Edit: The regions that I want to select are shown in this image (roughly, I selected them manually): http://i.imgur.com/4bpZLNJ.png It's ok if other blobs are getting selected too (I can filter them by their area afterwards).