Musāwāh arises when the number of transmitters in one's route equals that in the route of a known compiler up to the specified endpoint, even though individual narrators may differ.
Example: Suppose al-Nasāʾī has eleven links to the Prophet ﷺ in one report. A later scholar possesses another route to the same endpoint also containing eleven links. There is numerical equality with al-Nasāʾī's route.
The test is equality of counts and endpoint, not meeting a particular teacher of al-Nasāʾī. Hence musāwāh is distinct from muwāfaqah.
Equal link counts also do not entail equal grades of authenticity.