Aaron Rash, the YouTuber and Nirvana tone guru, has solved a mystery that has plagued him for four years – he has identified the electric guitar that Kurt Cobain used on Heart-Shaped Box.
Over the past few years, Rash has gone deep into the rabbit hole in search of Cobain’s tone secrets – particularly on Nirvana’s final studio album, In Utero. Rash has built his own guitars, swapped out speakers. He even got Cobain’s tech Earnie Bailey to help him build the Frankenamp that was used on the recording.
He says he is now working with Bartolini on some electric guitar pickups to help him on this journey. There is much he has learned along the way.
But the Heart-Shaped Box guitar has eluded him. Until now. His latest video reveals all. Why is Rash doing all of this? Part of it is nostalgia.
“When I hear In Utero, it brings me right back to being a kid,” he admits. Part of it is he simply cannot stop doing all of this. The In Utero bug is one he can’t quit. “I think it’s a really beautiful and really gracious, appreciation of this one record, just showing how much it means to you this way,” he says.
But the nostalgia serves a purpose. It’s the smell test. Or in this case, the tone test. For someone who has dedicated significant time and treasure in the pursuit of understanding just how Kurt Cobain arrived at his electric guitar tone – building guitars, engineering the IR packs so you can recreate it at home – this is an essential part of his investigatory tool kit.
And after his last video, in which he called ‘Eureka!’ on his quest to solve the In Utero tone riddle, concluding that it was Phase II Univox Hi-Flier with a mahogany neck, Rash has been doing some reflection, and something smells off.
“I’ll admit. After my last video, I feel kind of stupid, because I’ve made, like, the most compelling love letter about this guitar,” he says. “The more I’ve dug into this guitar after that video, my whole theory on it being the In Utero guitar just started totally falling apart.”
Of all things, what sealed it for Rash was the sound of his Hi-Flier’s tailpiece. It has this sibilant ring to it that is not on the record. “It’s pretty extreme. It gets into the pickups, you can’t get it out,” says Rash as he strums quarter notes to demonstrate it. Rash A/Bs Heart-Shaped Box and Rape Me and concludes it has to be the same guitar. But what make, what model?
Back to the drawing board. Rash fished through his correspondence with the late In Utero producer, Steve Albini, whom he interviewed for his channel in April 2024. He checked his emails with In Utero engineer and Shellac bass guitar player Bob Weston, who said Cobain just played “his normal Fender”.
“Whatever the hell Kurt was actually recording with, it couldn’t have been the Jag or the Hi-Flier,” Rash argues. “Those have long tailpieces, and they ring. So the only short tailpiece guitars would have been the Veleno, the Ferrington, and the Mustang.”
It was not the Veleno. Rash has one. The aluminium-bodied electric is all over In Utero, only it’s not on Heart-Shaped Box. The David Ferrington custom build could be what Weston was referring to but Rash says that doesn’t sound right. “That leaves me with only the Mustang,” says Rash. Luckily, he has heaps of them. Literally, dozens. None of them have sounded right.
Then he had an epiphany. Rash was looking at a photo of Cobain with a Mustang, and where the lacquer and paint had been worn away, the exposed wood held a clue.
“This photo completely changed everything for me,” he says “That’s not Alder. That’s swamp ash.”
Rash admits he has owned 30 to 40 Mustangs in the course of this crazy project. Another one was not going to hurt. Rash ordered himself a swamp ash body to test his theory.
“It finally came, and I put it together, and literally the first chord I hit on it after I put it together just gave me goosebumps,” he says. “It was crazy… Four whole years I was trying to figure that out, and there it was in my hands.”
Does it the body wood make that much of a difference. Rash argues yes. He would not be alone. Paul Reed Smith would argue something similar, too. But Rash acknowledges that his latest epiphany is going to cause some controversy. There are those – such as Nashville-based musician and YouTuber Jim Lill – who quite credibly argue that tonewood has less to do with how a guitar sound.
Rash is undeterred. He says the swamp ash Mustang, i.e. the Heart-Shaped Box Mustang, has “such a woody, really wild voice that the other guitars don’t have”, and that Lill is yet to test swamp ash. To Rash’s ear, the swamp-ash bodied Mustang sounds totally unique. Earnie Bailey agrees. He told Rash that swamp ash was his favourite-sounding tonewood.
Rash might have identified the guitar that Cobain used to track Heart-Shaped Box. He has also opened up another can of worms. One thing is for sure; he isn’t done mining In Utero for all its tone secrets. There is more to come.
You can follow his journey on YouTube, and check out his In Utero and Nevermind IR packs at Aaron Rash.
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