Opeth had spent 20 years on the Swedish metal scene when they turned their attention to their 10th album. But 2011’s Heritage wasn’t more of the same – to the horror of some fans, they toned down the aggressive growling vocals and distorted guitars, and embraced the prog tendencies they’d always hinted at. That year, band leader Mikael Åkerfeldt talked us through the process.

You could say it was inevitable. Album after album, the death metal roots from which Opeth sprang were trimmed away, exposing a beautiful progressive rock blossom. And while the aggressive growls and heavy distortion were still tangible in albums as recent as 2008’s Watershed, there were always hints that a later release could erase their metallic inclinations.

Those hoping for a sign of brutality need only look at the cover of Heritage to give up. The artwork is an open invitation to a musical odyssey steeped in prog rock – a bountiful tree rooted from the depths of hell, built around a pastoral landscape, a flaming city in the background and a pit of skulls beneath. It’s a mammoth leap from the gothic imagery of yesteryear. Pure and simple, it’s Opeth’s proggiest album to date. Mankind might feel the tremors, but the leap is but a small step for frontman Mikael Åkerfeldt.

“It feels, without sounding pretentious, like we’ve been working our way up to this point since the first album,” he explains. “I did start writing stuff that sounded like a continuation of the last album, but I was kind of fooling myself. I had two songs and I ended up deleting them after Martin Mendez said ‘Man, that’s not good!’ He was on the same wavelength as I was, pretty much, I just needed a second opinion to get a kick up the ass. So I scrapped everything and started from scratch. The Lines In My Hand was the first song I wrote for Heritage, then I wrote the rest of the stuff in six or seven months and it was easy. I didn’t stop and think – I just wrote it.”

Be warned: Heritage is almost devoid of metal. Gone are the distorted guitar riffs and drum machine-style pedal action that leant itself to the Swedish death genre out of which Opeth were born. Clearly a brave step for a band who have been deemed heavy for 20 years; and possibly one that’s detrimental to their metal fanbase. “You can’t worry about those things,” Åkerfeldt says. “I think some fans will be disappointed – but we’ve done experiments in the past. If you know your Opeth history, this isn’t an outrageous album at all.”

Åkerfeldt essentially calls the shots, but there are four others in the merry band of brothers; and guitarist Fredrik Åkesson’s thoughts on the move from metal must be worth hearing. In fact, he’s in accordance with Åkerfeldt’s choice. “When I heard about the album I knew there wasn’t going to be any growls, and there’d be less distortion on the guitars and bass. The metalhead in me was like, ‘Are you really sure about that?’ but when I heard the stuff I was like, ‘Yeah, that’s a really cool vision!”

By shifting the focus from brutality to prog-drenched experimentation, Heritage opens up a new world to both fans and the musicians who play on the record. Without the oppressive effect of distortion, there’s leeway for other elements of the band’s sound to shine – especially for drummer Martin Axenrot.

“This time round everyone has their own space, especially Martin; he’s been aching to do an album like this fore ver,” says Åkerfeldt. “He’s only been known for his metal drumming but, he actually started out in a marching band and his drumming idol is Ian Paice. He’s never really had enough credit. So he’s all over this album doing rock, fusion, jazz and heavy metal. It’s great that every musician is there.”

Joining Opeth on Heritage are two notable guest musicians – Peruvian-born percussionist Alex Acuña from Weather Report and flautist Bjorn J:son Lindh, who’s worked with Mike Oldfield among others. “Alex was a bit of a coincidence,” says Åkesson. “A guy who was helping us with the drums knew we needed help with a percussion part, and also knew that Alex was in town for a drum clinic, so he told us about it. Alex is like, only the best percussion player in the world, so it was perfect!”

Lindh wasn’t so easy a coup; the band tried and failed several times to get him to play flute. But as he was in Stockholm when they were recording, he agreed to pop by.. Or As Åkesson puts it: “he did two takes then pissed off!” Perhaps unsurprisingly Lindh wasn’t the only famous flute player that Opeth had in mind for the record.

“I did email Ian Anderson but I never heard back. Funnily enough, when I went down to Steven Wilson’s place to mix the album, he says, ‘I just got an email from Ian Anderson. He just wants me to look into mixing Aqualung!’ But I’m really happy in retrospect that we have Bjorn, because it fits with the vibe of the record.”

One musician will not be revelling in the glee afforded by Opeth’s newest endeavour. Earlier this year long-standing keyboardist Per Wiberg left the band, the reasons for which may never be clear. Åkesson recalls Wiberg saying he’d “lost the joy of playing music” – but Åkerfeldt can’t help but feel there was something more personal involved: “I don’t think he felt comfortable with me having the final say on things,” says the band leader. “In fact, sometimes I felt like he despised me. He was calling up the other guys and going out to bars with them, but he never called me. We used to be really good friends.”

Animosity doesn’t make the task of firing someone any easier. Åkerfeldt recalls giving his dispirited keyboardist his marching orders: “I fired him, and I got terrible panic attacks after that. I was doing it through email because I was bitter and angry. Then we started emailing back and forth. He’d never said more heartfelt stuff than he did in those emails. So I asked him, ‘Would you have left anyway?’ and he said, ‘Yes’. That made me feel a lot better.”

He’s delighted with the contributions of ex-Yngwie Malmsteen keyboardist Joakim Svalberg. Although not necessarily a permanent fixture (Åkerfeldt prefers to “take things slow”) the new recruit is already proving a hit. Anyone in attendance at recent gigs will testify to his pristine vocal parts. “Our voices fit together better than Per’s,” Åkerfeldt says. “But then Joakim’s very professional in that sense. He’s not going to do anything half-arsed. He’s so prepared. He knows all the lyrics – even I forget the lyrics! – all the harmonies, and he’s really into it.”

The band are certainly making the most of Svalberg’s prowess. The opening bars of Heritage are a sparse and delicate piano piece more befitting a woeful interlude than an album’s introduction. But like the cover art, it serves as a blatant indicator that Opeth are doing something different this time. It’s more than just a ‘less metal’ version of the band; you’ll find cheeky folk ditties, vocoder passages and ominous tribal drums conveying menace in equal measure – but in an entirely different way than in the past.

“I’ve never been a big fan of happy, uplifting music. But I think sorrowful music can be uplifting,” muses Åkerfeldt. “With the production of this album it was easy to bring those things forward musically. If you do the metal thing, the few emotions that are in there come from aggression; this time it was easier to tap into more profound feelings.”

Talking tabout his thoughts on the state of the current music scene, it’s evident that he feels uninspired by today’s metal offerings. “We’re the biggest metal fans ever, and that’s why we get a bit pissed off. The contemporary scene doesn’t really offer me anything right now. I take all my inspiration from older bands.” Which might be why Heritage is their least metal album to date. Åkerfeldt’s musical interests include metal, jazz and folk, but he also attributes influence from a person who’s proved integral in Åkerfeldt’s professional and personal life.

“Steven Wilson played me an album by David Crosby that I hadn’t heard – his first solo album If I Could Only Remember My Name – and it blew my mind. It’s a jamming kind of record but it’s got the crème de la crème of the West Coast scene. Recently I went for what I like to call ‘an old man’s walk,’ where I go out and listen to music. I was listening to Rainbow Rising and my eyes were tearing up. I was like, ‘How is this possible? I’ve heard this a million times!’ Now it means more to me than ever. It’s those types of records – Rainbow’s Rising, Judas Priest’s Sin After Sin – I listen to a lot.”

There’s no doubt that Opeth will continue to reinvent their wheel at every turn. “A lot of people, once they have a career, get afraid of their own creativity,” Åkerfeldt muses. “They think they’re going to lose their jobs if they get creative. But I think our career is based on doing what we want, because that’s what we’ve always done.”

In July 1974, the 25-year-old Rick Wakeman had his first heart attack. The keyboard player, who had left Yes earlier that year following the tour for the divisive Tales From Topographic Oceans album, had been taken ill just a day after staging a show in support of his third solo album, the hugely successful Journey To The Centre Of The Earth, at the Crystal Palace Bowl in South London.

And so it was that he found himself stuck in Wexham Park Hospital in Slough, Berkshire for six weeks while he recovered. The heart specialist who was treating him advised him to stop playing and effectively retire. “I had been told that I would not be able to work again, and if I did my heart would give out,” Wakeman told Classic Rock in 2013.

Wakeman was having none of it. Defying doctor’s orders, he spent his convalescence sketching out the album that would become The Myths and Legends of King Arthur And The Knights Of The Round Table. The tale of the fabled British ruler had caught Wakeman’s imagination after being taken on holiday as a child to Tintagel in Cornwall, whose castle was said to be the site of Arthur’s court Camelot. A more recent visit to Tintagel had ignited the idea of writing an album based around the Arthurian legends.

“I was staying at the King Arthur’s Arms, and I was looking out at the ruins of the castle,” Wakeman told The Strange Brew. “I’d always been fascinated by the legends, but being there, in that atmosphere, it just felt like the right time. I wanted to do something that had a narrative but wasn’t just a retelling of a book. I wanted to pick out the characters – Galahad, Guinevere, Merlin – and give them their own musical identity.”

Cooped up in his hospital room, Wakeman began devouring books on the subject, scribbling musical ideas on manuscript paper and humming them into a cassette recorder someone had smuggled into his room for him. The very first song he wrote there reflected both his health issues and the medical advice that he should quit: The Last Battle.

“It’s not really just the last battle of King Arthur but it was probably my last battle because I wasn’t going to give in,” Wakeman later said of the song’s defiant title.

The album itself was no less ambitious. “Writing Arthur was different from …Six Wives,” he told The Strange Brew, referring to his second solo album, The Six Wives Of Henry VIII. “With …Six Wives, I was painting portraits of people I could research in history books. With Arthur, I was painting legends. The music had to be grander. I remember sitting at the piano and trying to find a theme that sounded ‘ancient’ but with a modern, progressive edge..”

Even at that early stage, he had big plans for both the record and a huge live extravaganza to accompany it – a King Arthur Day, held in the grounds of Tintagel Castle on Easter Monday.

“I’d like it to be more of a pageant than a rock show and involve the local people in making it a complete show, with jousting, medieval bands and knights,” he told Melody Maker journalist Chris Welch at the time. “It’s got to be planned in advance so we can cater for 100,000 people,” he added optimistically.

Wakeman began recording the new album in earnest at Morgan Studios, Northwest London in November 1974. He was joined by the so-called English Rock Ensemble – vocalists Ashley Holt and Gary Pickford-Hopkins, guitarist Jeffrey Crampton, bassist Roger Newell, drummer Barney James and percussionist John Hodgson. They were joined by narrator Terry Taplin. And then there was the 45-piece New World Orchestra and the 48-strong English Chamber Choir. The latter pushed Wakeman’s label, A&M, over the edge.

“The label thought I was mad. I told them, ‘I want an orchestra, a choir, a rock band, and narrators,’” Wakeman told The Strange Brew. “They said, ‘Rick, that’s going to cost a fortune.’ And I said, ‘Yes, but it’s King Arthur! It can’t be small.’ We were pushing the boundaries of what a concept album could be. It wasn’t just about the music; it was about the spectacle.”

Among Wakeman’s arsenal of keyboards was a Mellotron, which was duly deployed to evocative effect. “The Mellotron was essential for King Arthur…,” he told The Strange Brew. “It has that slightly eerie, haunting quality that fits the Lady of the Lake or the mystery of Merlin. I used the choir tapes and the string tapes to create this wall of sound that felt like you were in a great hall or on a misty battlefield. It gave the album its atmosphere – that feeling of being half-real and half-dream.”

The finished album delivered on the grand yet dreamlike atmosphere. From the mysterious, sombre drift of the opening Arthur onwards, it struck an enchanting balance between complexity and melodic heft, as surging Mellotrons and squelching Moogs collide with real choirs, vivacious orchestral interventions and the exhilarating of sound live guitars, bass and drums.

Wakeman certainly didn’t sound like a man who had recently had a brush with death. His synth solo on Sir Lancelot And The Black Knight is one of the most outrageous things he has ever recorded, not least the moment when its underlying pulse is hijacked by a brief burst of hip-shaking samba.

Elsewhere, a labyrinth of layers and contrasting keyboard tones gave the ominous Merlin The Magician an ethereal quality in keeping with the mystical overtones of the King Arthur story, while the pomp-fest of The Last Battle is 10 minutes of euphoric grandeur.

The Myths And Legends Of King Arthur And The Knights Of The Round Table was released in March 1975. Although it didn’t replicate the phenomenal success of Journey To The Centre Of The Earth, it still did more-than-respectable business on both sides of the Atlantic, reaching No.2 in the UK and No.21 in the US. And while Wakeman’s vision of a huge King Arthur-themed gig in Tintagel never materialised, he did something arguably even madder: a live show… on ice.

After Wakeman’s suggestion for a one-off gig at Wembley Stadium was deemed too ambitious, they settled on the smaller Wembley Empire Pool, which stood nearby. Three shows were planned between May 30 and June 1, 1975. There was just one problem – it had been booked by an ice dancing troupe for a show due to start immediately afterwards.

“I wanted to do the King Arthur… show at Wembley,” Wakeman told Classic Rock. “And they said: ‘You can’t, there’s an ice rink installed.’ I said: ‘Sod it, I’ll do it on ice.’”

Funded by Wakeman himself, the resulting shows were either one of rock’s most unique spectacles or its grandest folly. As well as the English Rock Ensemble, the keyboard wizard was joined by an orchestra, a choir and a small army of more than 60 skaters playing various characters from the King Arthur story, from Arthur and his paramour Guinevere to a phalanx of knights.

“I wanted the concerts to be musical and entertaining,” Wakeman told Metal Talk. “I followed some great advice given to me by David Bowie, who told me to do what I wanted to do on stage, especially if I was using my own money. ‘Don’t let any promoter, agent or manager tell you,’ he said. ‘They don’t have the imagination…’ I’m forever indebted to David for that.”

The sold-out shows were ridiculously entertaining, but they were also hugely expensive to the point of wiping Wakeman out financially. He managed to tour the US and South America – albeit without the ice rink – but it wasn’t enough to reverse his parlous fortunes. He had only one option: rejoin Yes. By the end of 1976, he was back in the band he’d left two years earlier.

Today, The Myths and Legends of King Arthur And The Knights Of The Round Table stands as one of the high points of both prog’s Golden Age and Wakeman’s own career, even if its own legend has been overshadowed by those infamous, ultimately ruinous gigs.

But it was just as important for Wakeman on a personal level, a blast of symphonic defiance in the face of both medical advice and even death itself. Looking back on the Wembley gig, he recalled playing The Last Battle – the song he’d composed while convalescing in hospital and ignoring his doctor’s insistence that he hang up his cape.

“I vividly saw myself lying in bed at Wexham Park Hospital, absorbing the consultant’s unwanted advice that I should contemplate early retirement,” he later said. “It showed the piece had far more subconscious meaning than I’d realised when I wrote it. It was, in retrospect, as much about me as about events at Camelot.”