Today marks the 30th Anniversary of the release of Soundgarden’s blockbuster album Superunknown. It debuted at #1 on the Billboard 200 album chart, edging out Nine Inch Nails’ landmark album The Downward Spiral (released the same day), and it went on to sell nearly 10 million units. Soundgarden collected two Grammys from the album, one for the superb rocker “Spoonman,” and the other for the haunting classic “Black Hole Sun.” The latter is probably Soundgarden’s best known song. An enduring symbol of singer Chris Cornell’s ingenious songwriting, it’s enigmatic, foreboding, triumphant, and intoxicating — all at the same time.

We’ve all heard “K-pop” used as a catch-all term for boy/girl “idol” music emerging from South Korea. Colloquially, K-pop invokes the notion of an entire cultural ecosystem built around carefully manufactured star performers working in a hybrid mélange of music, dance, and fashion. As we’ve witnessed in recent years, the global audience for K-pop has exploded, with acts like BTS, Blackpink, EXO, Twice, and NewJeans attracting massive, obsessive fanbases outside of Korea, and even topping US pop charts. Is there something special about K-pop music that distinguishes it from, say, Western pop? What makes K-pop sound like K-pop?

When talking about music composition, Lou Reed once said, “One chord is fine. Two chords is pushing it. Three chords and you’re into jazz.” Maybe that quote is apocryphal, but it’s amusing, nonetheless. Putting aside the exaggeration, Lou Reed was making a perceptive argument: You don’t need a lot of sophisticated harmony to create an emotionally moving song. Indeed, it takes impressive skill and imagination to compose an evocative song that employs only one or two chords.

In January of 1983, Def Leppard released their massively influential third album, Pyromania. It’s a masterpiece — made of equal parts hard rock and radio-friendly melodic pop, fusing the raw crunchiness of AC/DC with the tuneful, painstaking sophistication of Boston. Forty years ago this week, the album’s lead single reached its peak on the Billboard Hot 100 (#12) after hitting #1 on the Mainstream Rock chart. That single, “Photograph,” perfectly encapsulates all the maximalist elements that combine to make Pyromania a truly transcendent album. On this 40th anniversary, let’s dive deep into the song’s composition and production elements to explore how it all works.

Brace yourself. It’s that time of year, which means Mariah Carey’s enduringly popular Christmas tune is back in your life, either by invitation or not. Unquestionably, this 1994 song has joined the time-honored canon of Christmas standards, alongside classics like Mel Torme’s “The Christmas Song” (1945) and Vince Guaraldi’s “Christmas Time is Here” (1965). In fact, Billboard now ranks Mariah Carey’s “All I Want For Christmas Is You” as the #1 holiday song of all time — and as of this week it’s the #1 song in America for the fourth straight December. Stereogum’s Chris DeVille once rhetorically asked if this song is the only true Christmas standard to have been written in the last 30 years. I believe the answer is “yes.” Why has this particular song managed to achieve such status? Let’s figure it out.

In 1982, Los Angeles-based supergroup Toto released their 4th studio album, fittingly named Toto IV. This month marks the 40th anniversary of the US release of the second single off the album, and the band’s best-known song, “Africa.” It’s a tune widely loved for its smooth melody and indelible hooks, but also variously reviled—for factors usually having nothing to do with music. In recent years, this pop jam has managed to reach mega-meme status, and at present it is approaching 1.3 billion streams on Spotify (making it one of the most played songs of the 20th Century). In fact, today the song may be more popular than it was in 1983 when it hit #1 on the Billboard Hot 100. For all the cultural baggage it carries, “Africa” is a truly innovative, masterfully crafted piece of music (which is saying something given that it’s not even the best song on the album!). Yet we so often see the song reduced to droll memes, or dismissed simply as a superficially dramatic (albeit catchy) pop tune. As famous as the song has become, it seems most people really don’t appreciate the brilliance of its musical architecture. But make no mistake: It is brilliant. Let’s check it out.

So far, this column has mainly dealt with pitch-centered music, focusing on harmony and melody. With hip-hop, we generally consider pitch to be of secondary importance, with rhythmic content being primary — which is why rap music often gets short shrift when discussing music theory. This dismissive attitude towards rap music has been pervasive in academia, but the attitude is changing. Hip-hop contains vital musical constructs not commonly found in other forms of music, and these innovations represent phenomenal artistic achievements. Those of us who work in orchestral, jazz, rock, folk, etc., can gain a lot from really listening to, and engaging with, hip-hop.

Anyone who has heard the music of Silk Sonic, the R&B superduo comprising Anderson .Paak and Bruno Mars, will immediately recognize that it’s heavily steeped in early-’70s soul aesthetics. From just the first two singles, “Leave The Door Open” and “Skate,” there’s no doubt that the Silk Sonic project is part homage, part parody — and clearly self-aware. But if you can get beyond the devilishly smooth retro façade and tongue-in-cheek lyrics, you’ll find that the tunes contain truly challenging and inventive musical constructs. While Mars and .Paak are plainly channeling the refined harmonic language of Stevie Wonder and Holland-Dozier-Holland, it would be foolish to dismiss this effort as a mere nostalgic indulgence. Silk Sonic may be superficially steeped in the 70s, but they’re also forging new paths compositionally.

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.

Vivek Maddala is an Emmy-winning composer and a regular participant in The Number Ones Comment Section. After reading his takes on the music theory behind several historic hits, we invited him to turn his focus on more current singles. Welcome to our new column In Theory.