re:member does curious things. The fourth 'official' solo album by Ólafur Arnalds takes the listener through varied moods and feelings, through different musical landscapes. You can hear every facet of his work -- the composition, the soundtracks, the pop -- bursting through, flowering. When the track unfold opens with what sounds like a stream skittering across rocks, it seems apt, because re:member keeps on moving, never tiring or letting the listener get tired. re:member is an album you can't forget, because every time you hear it something new and wholly unexpected emerges.

"This is my breaking out-of-a-shell album," Arnalds says. "This is me taking the raw influences that I have from all these different musical genres and not filtering them. I always have my hands in many different projects at once, and I feel that this album represents that."

The album is new departure because when Arnalds last finished touring, he decided he was not going to play live as a solo artist until he had something completely new to perform. He was inspired in part by his experiences playing shows with Kiasmos, his experimental techno duo, with Janus Rasmussen. "To experience the sheer unfiltered joy of being on stage, seeing crowd smiling and dancing and jumping -- that's the feeling I wanted to bring to my music."

Yet part of the reason for the eventual sound of re:member stemmed not from Arnalds' mental drive, but physical exigency. At the heart of the album are Arnalds' self-devised Stratus Pianos -- two self-playing, semi-generative player pianos, triggered by a central piano which he plays -- an invention born of necessity rather than experimentation. "I got into a little accident and I had nerve damage in my hand," he says. "I couldn't play the piano for a year, and I wasn't sure if I would ever be able to play again. It was completely petrifying." Years before, he had supported Ryuichi Sakamoto on tour and seen the great Japanese musician use self-playing pianos, and he mentioned to a friend that Sakamoto's set-up was what he needed. "It started as a joke, but I went home and started thinking: maybe there's something here -- not a crutch, but a creative tool. The spark of the idea came from me not being able to play, but it developed into something completely different."

With his friend Halldór Eldjárn, Arnalds set about developing the Stratus system: software that sends instructions to two pianos, "and the two become one and play together." Arnalds sets the values that the software feeds to the pianos -- the rhythm, the tempo -- and those are triggered by chords or notes he plays.

What happened when Arnalds started making music using Stratus was a little unexpected. It summoned its own mood and quickly became the focal point of his new compositions.

Arnalds' album evolved under the influence of a number of collaborators -- friends from different areas of music that came by his studio in Reykjavík and left a lasting mark on the album. One of them was hip-hop producer BNGERBOY, who's innovative sound caught Arnalds' ear and influenced the direction of the album -- "The track brot, which is orchestral, began with his beat. I started writing chords on top of it. But I ended up removing the beat left only the orchestra. That track would never have existed without him, even though he's not on it. But some of his sounds can be heard in other parts of the album."

That's fitting, because the title of the album -- and its lead single -- refers in a way to the act of creation. "re:member is about becoming a member of yourself again which I feel my journey for this album was, very much so. I was discovering all these different sides of myself, my creativity, my taste and interests." Nothing he does is discrete or partitioned off -- be it soundtracks like his BAFTA-winning score for Broadchurch, reinterpretations of classical music such as The Chopin Project with Alice Sara Ott, collaborations such as Island Songs, in which he travelled around to seven different Icelandic locations, collaborating with different artists, including Nanna Bryndís from Of Monsters and Men, to make a song and video from each place. Instead, everything is part of a greater whole. Arnalds says of his career: "I believe it is all the same piece of music. I never really start from scratch; I am always building on what I did before."

The title track re:member embodies both that idea of Arnalds' music being a continuum, and his desire to strike out for new terrain. It was hard work for him: though he built it around the Stratus, it still took three weeks of solid work before he had even the basic structure. "It became very personal to me," he says. "It starts with just one piano, which sounds a little bit like the music I had been making before, then it introduces one by one new elements and leaves the old behind. It takes us through the journey I was going through creatively, wanting to leave the past behind and see where else I can go."

Nevertheless, those who have loved Arnalds' music over the last 10 years need not be shocked. re:member is still distinctively Arnaldian, still forged of that alloy of melody and texture that has always been the key part of his art, where composition and production go hand in hand. "Sound and melody are completely equal," he says. "Melody doesn't exist without sound. It sounds simple when you say it out loud, but it isn't that obvious. Composers often write with a pencil on paper, and at that point the melody is just an idea." What makes it into something that can generate an emotional response is its translation into sound, which is why Arnalds has always thought like a recording engineer as much as a composer. The point at which it becomes preserved is the point at which it becomes music, and so every single sound must be pored over: how will the song sound if played on a Steinway concert grand as opposed to on the Pianette he bought in a secondhand shop for $150? "That's how I think in the studio, and I apply that thinking to every single element I write. I start with the point of view of the engineer: how does this sound?"

15 years ago, when he started writing music, Ólafur Arnalds was composing for imaginary films -- "I was scoring the pictures in my head." He didn't imagine anyone else would want to hear the music for those inner visions. Now he's one of the world's most popular composers, people very much do want to hear the music he hears to accompany his own mental movies. With re:member they will hear the most remarkable and beautiful expression of that music yet.