You should have a look at the 13 scariest pieces of classical music for Halloween, assembled by Limelight Magazine. It is hard for me to select a favorite, but I will point to this classic Disney cartoon of Saint-Saens Dance Macabre:
Saint-Saëns’s creepy 1874 tone poem is a Halloween classic, depicting the revelry of the Grim Reaper at midnight every year at this time. With his cursed fiddle, Death summons the dead from their graves to kick up their heals until dawn. In this vintage Disney animation, listen out for the xylophone sound of rattling bones.