If I may add: Sound wise, only a few razors will sing on the strop (I think 3 of mine sing and that is it). And if all of your razors sing, it is likely and indication that the spine is coming off the strop, and the singing is the free vibration of the blade itself on the leather. Eeek!
So likely, you dont want to hear the blade sing, and that could be an indication of a bad thing!