Katy Perry's Prism is strongly influenced by Sweden.

The "Unconditional" singer started work on her fourth studio album in her home town of Santa Barbara but Swedish producer, Klas Ahlund says working with her in his home country helped bring a different feel to the record.

"We did most of our stuff actually in Stockholm and I totally think that affected how it came out. When you move around the planet, the vibe of the place you're making the music in definitely makes an imprint on whatever you're writing," Ahlund said.

According to Ahlund, it was the stark difference between American and Swedish folk music that impacted on Katy's work - and he believes the "melancholy and lonely" tones of traditional Swedish melodies combined with Katy's bubbly persona were the lightening force behind the new album; inspiring songs such as "Roar."

"I hear American folk music as more of a communal thing where you sing along and you stomp your feet and dance to it. The Swedish melodies are more meant to sing on a mountain top with a bunch of goats - it's very melancholy and lonely. So when you infuse those things, when you bring a very strong personality and performance-based energy to a very strong melody then you get the best of both worlds."

While Katy's third album may have surprised fans with its more downtempo tracks, she says it was her intention for it to be a more reflective work: "The reason why I called this record Prism is because I actually finally let the light in and then I was able to create all these songs that were inspired by letting the light in and doing some self-reflection and just kind of working on myself."

Prism is available for purchase now.