It's easy to imagine Konami's Castlevania series as a large group comprised of smaller family units. When you look at those families, you start to see clear resemblances: The chunky sprites and riotously-colored backgrounds of Castlevania through Castlevania III, the shared monster designs between Rondo of Blood and Symphony of the Night, the dark, detailed environments of MercurySteam's games, and so on.
But if the Castlevania games share genetic material between them, Super Castlevania IV for the SNES is the outlier, the mailman-sired bastard who stands at the edge of his brown-eyed family and stares at them with blue eyes. No other Castlevania game looks like Super Castlevania IV. No other Castlevania game plays like it, and no other Castlevania game sounds like it.
Castlevania IV is a remake of Simon Belmont's first vampire-whipping adventure, though English-speaking players were made to believe Dracula had simply risen again after the events of Castlevania II (like he does). The discrepancy is of little consequence, since the premise for Castlevania IV is as basic as they come: You, as Simon, need to put Dracula back to bed.
But while Simon's vampire-hunting tools are familiar in Castlevania IV, the manner in which he wields them isn't. He can whip in eight directions. He can use his weapon as a makeshift rope to swing over gaps. Most intriguingly, he can dangle his whip (hee hee) to inflict minor damage on enemies, or shield himself from projectiles. When you consider how the Vampire Killer is supposed to be a blessed weapon, the idea of it damaging monsters with a mere touch actually makes sense.
Regardless of whether you view Castlevania IV as a reboot or a continuation of Simon Belmont's personal legacy, the game is a weird (graveyard) duck. Its specific brand of monster designs never pop up again in any subsequent Castlevania games, nor do Simon's unique fighting methods.
And, again, Castlevania IV's musical score is unlike anything you'll get from its cousins. Sure, it contains reprises of classic themes from the series, including Vampire Killer, Beginning, and my favorite rendition of my favorite Castlevania song, Bloody Tears. It's that familiarity, however, that makes it easy to notice how expertly Castlevania IV's score makes use of its bass and, most notably, kettle drums.
The launch year for the Super Famicom / SNES was a nice time for game music. No doubt sprite artists appreciated the SNES's extensive color palette, but I can only imagine game music composers broke down in tears when they first experimented with the legendary richness of the console's Sony-produced soundchip. Castlevania IV's soundtrack was composed by Masanori Adachi and Taro Kudo (both of whom still perform sound design for games), and I like to think they went at Castlevania IV's soundtrack with the gusto of a kid entering a room full of instruments for the first time. Like, "Hey! Is this a kettle drum? Man, I am going to use the hell out of this!"
Maybe that's why at least 60% of Castlevania IV's soundtrack is backed up by the lovely sound of rolling thunder. And I believe the drum is put to its best use in the track In the Castle, which accompanies Simon as he finally climbs the steps to Dracula's domain.
See, Castlevania IV doesn't start you in Dracula's foyer like the first Castlevania. It doesn't even start you somewhere in the middle of the Transylvanian countryside like Castlevania III. You start off at the edge of Drac's sprawling estate and work your way in. You go through the stables, through gardens, up waterfalls, and through lesser mansions. Castlevania IV is a good reminder that the lords of medieval European castles usually owned the land for miles around in addition to the castle itself.
If you get past the hazards and minions patrolling outside Dracula's walls, you're finally allowed access to his courtyard, which is where In The Castle thunders at you. The track is hauntingly pagan and obviously meant to imitate a war drum. Fittingly, the courtyard is stuffed with enemies gifted with an insane spawn rate. If you're not careful, you might find yourself overwhelmed. It's your last push before you enter the gate, and In the Castle infers the vampire king is mustering his forces for a final attempt to stop your hunt in its tracks.
But you'll prevail. You're Simon Belmont, legendary vampire hunter. You must prevail. Otherwise you won't get to hear the intense majesty of The Room of Close Associates, or Dracula's menacingly mellow battle theme.