Deciphering the Tension in Deltarune's Battle Theme

It was nearly two weeks ago when Toby Fox blindsided the world with the first chapter of Deltarune, a free, three-hour demo of his next game. I’ve spent no small amount of time in the past few years wondering how I would possibly react to whatever Toby Fox did next. Would his quirky sense of humor still land on me a second time? Could Undertale’s twists ever be successfully recreated? I wouldn’t have guessed it, but it’s turned out to be a resounding yes on both counts. Sometimes, lightning really does strike the same place twice!

I’ve been reflecting on (or obsessing over?) my time with Deltarune ever since. Talking to friends, hunting down fanart, wiki-crawling, and more than anything, keeping that soundtrack on heavy rotation. In my unending hunt for more secrets, there was something on the track list that stood out to me: why would the game’s battle theme be given the name “Rude Buster,” the same name as Susie’s signature ability? I didn’t quite understand at first, so like any normal fan would, I listened, listened, and listened again until I finally started to understand. Feel free to take a listen yourself, and let’s dive in:

“Rude Buster” evokes a decidedly dangerous feel with its devilish harmony of piano chords and bass. In the song’s opening seconds, their heavy syncopation emit energy and excitement, almost in mockery of its unsettling minor key progressions. It makes a strong impression! Even when the melody breaks at 0:27, these two instruments remain at each others’ side, forming a sound, unbreakable foundation.

It’s not long before the tension is ramped up by the addition of a synthesized string hook. Its melody is layered on top of the core foundation, ever so briefly mirroring its tonality and then soaring high above it as it seizes control of the song. When the melody breaks, the lead enters a temporary period of harmony with the underlying rhythm before leaving the song entirely afterwards. Undertale fans, did you recognize the motif here? The break at 0:27 is a sped up version of “Determination,” the game-over music (and a core motif) of the first game!

The tension hits its climax in the final phase of the song (0:47), where the smooth lead synth gives way to a Sega Genesis-esque FM synthesized guitar solo. The tempo of the solo starts slow, but quickly builds to outpace even the syncopated rhythm line. It gives the song a definitive edge in a brief period of barely-restrained chaos. Only two other songs in the game feature such dominant use of FM synthesized guitar, and guess what: they’re the two songs specifically designed for Susie (“Susie” and “Vs. Susie”). I don’t think it’s much of a stretch to say that we’re intended to tie the use of the instrument to the character herself!

Kris visits Susie at the cookie stand she temporarily runs while partnering with Lancer. 'All proceeds go to kicking your ass,' she says.

So what is the use of guitar in the battle theme meant to tell us? I’m not looking to put words in Toby Fox’s mouth, or assert any singular “canonical” meaning, so let’s be clear: this is (and has been) strictly my own, personal interpretation. The distinct phases of “Rude Buster” shift its feel from teetering on the edge of harmony, to conflict, to a more resonant harmony, and then back to even greater conflict. It’s not unlike Susie herself! After all, the first chapter of Deltarune is in many ways about discovering who Susie is and where her true intentions lie. The dramatic tension in the song matches the tension she feels within herself. You could easily go on to say that the constant harmony of the rhythm section (the piano chords and bass) mirrors the natural understanding that exists between Kris and Ralsei. This sense of progression and resonant flow of melodies is, in my eyes, what makes the song such an excellent battle theme, even after hearing it over, and over, and over.

There are a lot of obvious reasons why I’m excited for Deltarune’s story to pick back up sometime down the road, but one thing I’ll be keenly looking forward to is what happens with the battle theme in Chapter 2. Maybe it’s just me, but I have a distinct suspicion that it’s going to be something new! And if that’s the case, could that mean that we’ll have even more new, thematically appropriate battle music for every chapter of the game? While I’m left to speculate rampantly, Toby Fox is no doubt confronted with an intimidating and difficult path forward. Until then, I’ll be cheering him and his new team on with my utmost respect, confidence, and enthusiasm.

Even More “Rude Buster”

If you care enough to read a blog post about “Rude Buster,” you might be interested in some covers, too…? Carrying on in the spirit of the Undertale fandom, the musicians of the community are already going all-out with Deltarune covers. Here are a few of my favorites so far: