Hassidic Music: Lubavitch

[robert wiener <wiener...>]

I had heard that in the last years of the Lubavitcher rebbe's life,
when he would appear in public his followers would sing a song.
Perhaps its name was "Hamelekh Hamashiakh".

Does anyone know if that is true?  If so, was the song recorded and
was there a recorded version "accepted" by the community?

Bob Wiener