Progressive Metalers Opeth Playing Wellmont Theatre on April 19

Opeth is daring heavy and progressive metal and rock fans to expand their definitions of the genres. The powerful and experimental Swedish band, supporting its latest album, “Heritage,” performs on Friday, April 19, at the Wellmont Theatre.

“I want to challenge metal fans by asking, “what is metal to you?” said singer-guitarist bandleader Mikael Akerfeldt. “I have a knowledge of metal and I feel like I have the right to state that question and develop my own form of  metal.”

Over the course of a 10-album, nearly 20-year career, Opeth have refused to conform to heavy metal’s tried-and-true formula of crashing power chords, searing guitar solos and pound-you-into-submission drums. Instead, the band impresses with sweeping, adventurous and complex compositions that twist and turn from heavy prog and metal parts to folk and spacey passages, with elements of death metal and jazz thrown in for good measure.

 “The general idea of metal is that it has to have distorted guitars and screaming vocals, a heavy production and certain imagery and the band’s supposed to look a certain way,” Akerfeldt said. “But metal for me is something else too, it’s a form of rebellion.

 “Nothing should box you in,”  Akerfeldt said. “Following the norm in a metal context is no better than being a manufactured boy band.  When people say “Heritage” is not a metal record I wonder what they mean. I think as a band we’re looking at the tradition of all metal and hard rock instead of trying to fit into the contemporary metal environment.”

On “Heritage,” Akerfeldt eschews growling vocals for clean singing and, while there are plenty of prog-metal riffs to keep headbangers happy, there are many light moments, including piano interludes and mellow, atmospheric soundscapes.

Akerfeldt said the band’s foray into a more experimental direction on “Heritage” was a natural progression . “I didn’t feel that I had more to give in terms of the sound that you heard on the previous records,” he said. ‘“Watershed” [Opeth’s previous release] was the pinnacle of that style. I tried to do something else and I was really happy with it. “Heritage” is a monumental record.”

While Opeth has progressed exponentially from its 1995 debut album, “Orchid,” Akerfeldt said he is extremely proud of the band’s entire catalogue.

 “There have been so many changes and I’ve changed too as a person,” he said. “With some old songs I think, “did I do that?” I have no memory of writing it and I’m shocked it still holds up.  As much as we’ve changed, I’m really proud of our body of work. There’s not an album that I feel ashamed of or a song that I want to re-record.”

Though he grew up in the Eighties and lives in the digital age, Akerfeldt, 38, is a devotee of Seventies prog-rock and boasts an extensive vinyl collection including many obscure releases. As a musical purist, Akerfeldt said he loves becoming immersed in an album and tries to give Opeth fans the same experience. He shudders at the thought of people buying one or two songs off of an Opeth album on the Internet.

“I get irritated. I can’t relate to it,” Akerfelt said. "I’m very traditional when it comes to albums. I want to hear the music the way the artist intended it to be heard, the sequence of the songs, the flow, the concept of the record. I don’t listen to music like kids do these days.  I have three daughters with zero patience for listening to entire albums and it just annoys me.”

The band’s current headlining tour with fellow Swedes Katatonia is the band’s last road jaunt for “Heritage,” which was released in September 2011. Akerfeldt said he’s already written three songs for the next Opeth album.

“One relies heavily on  vocal melodies and I think I did a good job,” he said. “Another came from a bit of a band jam on this tour. It’s like a tribute to the band Goblin [Italian Seventies prog-rock].”

It’s the third song that will most have Opeth fans salivating in anticipation, based on Akerfeldt’s descprition. “It doesn’t have a set structure,” he said. “I kind of piece things together, a cluster of different ideas, and it makes sense. It’s 10 minutes already and it’s not finished. It’s going to be a big,  crazy, epic piece.”

 IF YOU GO: Opeth and Katatonia, 8 p.m. Friday, April 19, Wellmont Theatre, 5 Seymour St., Montclair. Tickets are $25 advance, $30 day of show. For more information call the box office at 973-783-9500 or visit www.wellmonttheatre.com.