This Friday is the 30th anniversary of Nirvana’s groundbreaking Nevermind, an album that forever transformed the pop music landscape. The album’s furious rock anthems “Smells Like Teen Spirit,” “Come As You Are,” and “Lithium” made everything else being played on the radio at the time seem scrawny and frivolous by comparison. In the ensuing three decades, countless words have been written about how Nevermind mainstreamed the sound of grunge by emphasizing emotional delivery over tonal precision. And music journalists have spilled gallons of ink — real and digital — describing how Nirvana’s loud-soft-loud formula drew from punk and alternative rock (e.g. Pixies), hard rock (e.g. Boston), and early metal (e.g. Black Sabbath), while inaugurating new levels of dynamic contrast. So there’s no need to examine any of that here. Instead, let’s focus on something rarely discussed, but extremely vital: Kurt Cobain’s harmonic language.

Indeed, the most revolutionary facet of Nevermind is its almost complete abandonment of principles of functional harmony — principles that had formed the basis of essentially all Western popular music that came before it. In doing so, Nirvana effectively expanded the possibilities of what was allowable for songwriters operating within the pop mainstream. Kurt Cobain changed the trajectory of popular music by making it safe to eschew the traditional tenets of Western harmonic relationships, principles that trace their roots to Europe in the 18th Century (and arguably earlier). While it may be a stretch to describe Cobain as the Arnold Schönberg of rock music, his modus operandi (like that of Schönberg) was to create meaning and coherence without relying on established musical conventions.

“In Bloom,” the fourth single off of Nevermind, is a marvelous example that contains within its compositional makeup a vast repository of innovative non-functional harmonic structures. Let’s check out the song.

Functional Harmony

Before we dive into “In Bloom,” we should define some terms. Harmony is the sound created by combining notes to create chords, and diatonic chords are ones that are built by combining thirds (1.5-step or 2-step intervals) on top of different degrees of a given scale. Functional harmony is the idea that different chords in a given key center have predefined jobs to do, relative to one another. It’s a way of thinking about the roles that chords play as though they’re characters in a story. The protagonist, the comedic foil, the love interest, the antagonist, etc., each have one or more functions in a narrative story. In functional harmony, chords operate the same way. This is why we can often predict what chords are likely to come next when listening to a song that uses functional harmony, even if we’ve never heard the song before. Importantly, most examples of functional harmony follow some form of tension and release, where there’s a stable chord that feels like “home,” and different kinds of harmonic motion move away from stability before returning back home. (See Figures 1 and 2.) For more on this, check out the previous In Theory columns.

You’ll notice that each chord serves a particular function, forming a deliberate “story arc” following Circle of Fifths relationships. The tritone diversion serves as a kind of harmonic lubricant for smooth voice leading between the V and I chords. All the chords in the above example are diatonic, except for the tritone chord (G♭7♭5). Most of the Great American Songbook follows these sorts of functional harmonic relationships.

In short, functional harmony is a set of assumptions about how chords should behave relative to each other. A research paper published in the Annals Of The New York Academy Of Sciences titled “Neurobiological Foundations For The Theory Of Harmony In Western Tonal Music” goes so far as to posit that the principles governing functional harmony are hardwired in human physiology and cognition. While that’s a riveting topic, it’s one we can explore or debate another time.

Non-Functional Harmony

This is a fraught subject as there’s little agreement among composers as to what non-functional harmony actually is. Indeed, it’s more clearly defined by what it isn’t. Non-functional harmony is a structure wherein the chords simply don’t perform their traditional functions (as outlined above). A composer using non-functional harmony might choose chords based on their color, weight, or texture — but not based on their function. An analogy might be a visual artist who selects their color palette on the basis of each color’s intrinsic beauty, rather than on each color’s utility in painting a particular image.

On “In Bloom,” as with the other songs on Nevermind, Kurt Cobain created chord sequences and attendant melodies in a manner that seems completely out of step with the chords’ traditional functions. Orchestral composers like Debussy, Copland, Hindemith, Bartók, and atonal composers of the Second Viennese School had been utilizing this idea for quite some time — as had jazz composers like Wayne Shorter, Herbie Hancock, and John McLaughlin. But in 1991, to hear it in a Billboard Top 40 song was quite rare. And Nirvana did it practically in every song.

Chromatic Mediants

Frequently, Kurt Cobain utilized harmonic sequences that moved by a Major or minor 3rd interval, but in a manner that does not comport with predictable chord behaviors that progress between instability and stability. When two chords have root notes that are a Major or minor third apart and contain a common tone, this is an example of a “chromatic mediant” relationship. The verses of “In Bloom” represent a particularly curious case of the use of chromatic mediants. See Figure 3 below.

The C♭5-A5 turnaround following the B♭-G♭-E♭ sequence absolutely confounds me. I have no explanation for these seemingly nonsensical chords, so I have to assume Kurt simply selected the chords in a manner consistent with the idea of non-functional harmony: not due to any particular task they perform harmonically, but simply because he liked the sound of them (which I suppose is as good a reason as any). The I-♭VI-IV chromatic mediant sequence itself evokes an odd sense of mystery — and humor. So while it may not adhere to any predictable Circle of Fifths relationships, its “utility” might be that it just sounds cool.

“In Bloom” is not the only Nirvana song to employ this unusual chromatic mediant sequence. Another notable case can be found in the verses of their 1993 single, “Heart Shaped Box,” which also uses I-♭VI-IV. And the chord sequence isn’t exclusive to Nirvana. The best-known case may be found in John Barry’s James Bond motifs, which are threaded through his scores for the franchise. Famously, his “Goldfinger” main title theme, sung by Shirley Bassey, features the iconic I-♭VI pattern. Billie Eilishs “No Time To Die” channels the same vibe, using a variation: i-♭VI-IV-V7.2,3

On “In Bloom,” Kurt Cobain played the chords not as triads (containing the root, third, and fifth), but as dyads or power chords (containing only the root and 5th). This afforded him some melodic flexibility due to the chords’ ambiguous quality, where the listener would be unsure whether what they’re hearing is Major or minor. However, the D♭ he clearly sang in the verse melody (e.g., on the word “kids”) would necessitate that the B♭ chord is actually minor — but it’s not. There’s a peculiarity to the way Cobain fretted his power chords — with his third finger barring both the 5th degree and octave above the root (i.e., the third fret on the 3rd and 4th strings, in this case). When doing this, one must be careful not to inadvertently finger the third fret of the 2nd string, which is a D♮. But Kurt wasn’t careful, and throughout the verses you can hear that he occasionally sounded the D♮, making it clear the B♭ power chord is really a Major triad. This means the D♭ he sings in the melody over that chord, every time the verse cycles back to it, is actually a blue note.

Blues Tonality

The blue note is a chromatic note added to a pentatonic (5-note) scale, which results in a hexatonic (6-note) blues scale. In a Major pentatonic scale, the blue note is the ♭3, and in a minor pentatonic scale it’s the ♭5. Notably, “the blues” idiom doesn’t observe the traditional Major/minor dichotomy that is so fundamental to Western harmonic theory. In some respects, we can think of blues tonality as being in its own category, separate from traditional European-based harmonic language. If we were to follow the rules of Western harmony, the D♭ Kurt sang over the B♭ Major chord would create a kind of “tonal rub” — a dissonant sound. But it doesn’t sound dissonant because it follows an alternate system of consonance. This alternate system combines elements of both traditional Major and minor intervals where the rigid line of demarcation between the two is blurred.

Often, in blues-based music you’ll even find what we call a “neutral” third — one that’s neither strictly Major nor minor, but a little of both. A great example is Aretha Franklin’s vocal performance in “Respect.” The song is in C Major (or perhaps C Mixolydian), but when singing the lines, “What you want/ What you need,” she played with the intonation of the third by bending it variously up to E♮, down to E♭, and to several points in between. It’s what gave her performance so much vibe. Traditional Arabic music uses neutral thirds as well, as does a lot of American folk music. Some 20th Century composers like Charles Ives experimented with neutral thirds. On “In Bloom,” and throughout Nirvana’s catalog, Cobain sang neutral thirds often, scooping and bending the notes — which he was able to do without concern about clashing with Major or minor chords, given that he was working with the harmonic freedom afforded by the blues idiom.

Secondary Dominants And The Plagal Cadence

The song’s chorus is the only time we hear some familiar chordal roles we associate with functional harmony—albeit with some tasty surprises. See Figure 5.

After hearing the distant, unrelated chords that characterize the jagged, disorienting verses (see Figure 4, above), the chorus provides a bit of harmonic relief with a recognizable I-vi pattern (Figure 5). On the line “knows not what it means,” we hear an unexpected borrowed chord, the II7 (or the “V7 of V”): a secondary dominant. Here we can observe the Beatles influence Kurt spoke about in interviews. Following this, we hear another Kurt Cobain trademark, discussed above: the chromatic mediant relationship (with the C7 going up a minor third to E♭7). The chorus then resolves in a variation of what we call the “plagal cadence” — a IV to I resolution associated with church hymns. There’s something comforting about this cadence (think of the way the refrain of the Beatles’ “Yesterday” resolves), but Kurt’s use of the dominant 7 interval over the E♭ gives the chord a harder edge. It’s the cadence heard on the Beatles’ “Taxman.”

Neo-Riemannian Theory and the Sound of Grunge

There’s a school of thought related to non-functional harmony that seeks to make sense of seemingly unrelated chords — like what’s in the verses of “In Bloom.” It’s called Neo-Riemannian theory, and the idea is to connect triads through the lens of “transformational harmony.” The specific case that applies to Nirvana can be described as parallel transformation: converting minor chords into their parallel Major (or vice versa). One of the hallmarks of Kurt Cobain’s writing is his surprising use of Major chords where you would normally expect minor ones (e.g., B♭Maj instead of the more usual B♭min at the top of each verse). In fact, this characteristic is fundamental to what makes grunge sound like grunge.

As an experiment, try the following:

• Take a conventional pop chord progression you know, and change all minor chords to their parallel Major (e.g., Gmin becomes GMaj), while keeping all existing Major chords as they are; if there are any non-diatonic or half-diminished chords, for example, you’ll need to modify on a case-by-case basis; keep any upper extensions (9ths, 11ths, etc.) intact.

• Adapt the melody so it works with these new chords (which might result in an unusual “modal” sound).

• Now remove all thirds from the chords and play them as simple power chords, ideally with an overdriven (or edge-of-breakup) guitar sound.

Does it sound like grunge? Well, at the very least, it should sound grungier than it was before.

[If you’re a mathematician, you’re undoubtedly familiar with Riemann sums, a foundational principle in integral calculus. How cool would it be to relate this concept to Neo-Riemannian music theory? Sadly, I haven’t found a connection. Believe me, I tried.]

On this 30th Anniversary of Nevermind, let’s take a moment to appreciate Nirvana’s contribution to opening up the “Overton window” of harmonic language in pop music. Would today’s pop music still be as tethered to conventional principles of functional harmony had Nevermind not taken hold 30 years ago? Might other artists — perhaps Radiohead or Soundgarden or Alice In Chains –have pried open the door in a similar way? I suppose it doesn’t matter, because Nirvana did happen, and popular music hasn’t been the same since.