Michael Kiske has sung several times with the band. Examples are "Land of the Free" and "Time To Break Free", both from Land Of The Free, and "All You Need To Know" in To The Metal.
Hansi Kürsch also sung in "Land Of The Free" and "Farewell", both, again, from the same album.
Piet Sielck has a singing part in "Watcher In The Sky", from Powerplant. Subverted in that the song is taken from Iron Savior's album debut, on which Sielck has most of the vocals and writing credits.
What Could Have Been: According to Dirk Schlachter, "To Mother Earth", from Land Of The Free II, was going to appear in Majestic, the previous album.