Dr. Doom modified two pianos as secret weapons: Whenever Doom (or any other player) pressed a specific combination of chords, he could direct sonic blasts to kill everyone -or a specific person- either in the same room the piano is, or in a monitored room that he could see in a screen that serves also as music stand. Doom keeps one piano in Castle Doom, in Latveria, and the other in his Adirondacks fortress.
Doom used one of these pianos in a plot against the Fantastic Four when they raided Latveria. Initially, Doom intended to entertain the Fantastic Four as their guests, only to surprise them with an attack. However, Doom's minion Gustav Hauptmann tried to surprise the Fantastic Four and an agent of S.H.I.E.L.D. with an attack that would have also destroyed several works of art in Doom's Castle. Enraged at this disregard for culture, Doom used the piano to kill Hauptmann, then released the Fantastic Four.