E minor. G major. Repeat.

Those weren’t the chords that helped Nirvana conquer the world, but they were close. That simple two-chord progression makes up the majority of the band’s 1989 song “About a Girl,” made popular due to the MTV Unplugged in New York special that hit the airwaves in November 1994. By that time, band leader Kurt Cobain had been dead more than half the year, but the swan song Unplugged performance helped cement Nirvana as the premier alternative rock act of the ’90s.

And it all started with a few simple chords — E minor and G major. If you slide them up one half-step, you get F minor and A-flat major, two of the anchor chords in the riff of the band’s best-known song, “Smells Like Teen Spirit.” The chords’ proximity to each other has nothing to do with laziness on the part of Cobain’s songwriting, but, quite oppositely, his ingenuity.

“He couldn’t play — and had no interest in trying to learn — Eddie Van Halen speed scales or incredibly complicated jazz chords,” says the band’s one-time producer, Butch Vig. He would know; he helped cultivate the radio-friendly sound that spawned global success because of tunes like “Teen Spirit,” “Lithium,” “Come As You Are,” “In Bloom” and others. Vig recently talked to the Washington Post about Cobain’s legacy, which writer Chris Richards called “overlooked.”

It’s not that the songs aren’t well known. It’s that their creator possessed a gift for hemming simplicity into memorability, Richards writes. That might be why they were so popular on Internet tablature websites throughout their rise in the ’90s and eventual peak in the mid-2000s. Guitar tabs are a visual representation of the way chords and notes are played on the guitar neck itself, using numbers to correspond to frets and symbols to strumming and picking patterns. Because Nirvana’s songs made such heavy use of power chords — simple two- or three-finger patterns designed to achieve a chunky sound — their songs could be tabbed in mere minutes, then shared just as quickly.

It was Nirvana’s rudimentary songwriting that helped the songs become known worldwide as they are today. But it was also the equipment that helped shape the sound. Cobain famously played Fender models like the Mustang and the Jaguar, even more famously trashing them at the end of dozens of live shows. As long as there was a fresh guitar to be played (then subsequently destroyed), Nirvana was all set for a concert.

“The words came from his heart, and what was going on in the world around him,” explains David Locke, Owner and President of LAWKSTAR Guitars. “It was about the chord progressions, and how they matched the lyrics that he wrote. It really didn’t require someone playing this flashy guitar riff or being a showboat. The realness of his lyrics and a few cool chords took care of it.”

It’s been 20 years since Nirvana has existed in any form, not counting the mini-reunion at 2012’s 12-12-12 concert with Paul McCartney. However, the songs live on. And if the music’s any indication, it looks like we’ll still be remembering them in 20 more.