The maverick producer and the Italian composer have teamed up on a brave new project – with a little help from Jack White and Norah Jones

Nobody has ever accused Danger Mouse, aka Brian Burton, of being workshy. Since 2005's The Grey Album, his widely lauded hybrid of the Beatles and Jay-Z, the maverick producer has defined creative restlessness. There was Gnarls Barkley, with Cee-Lo Green, which spawned the multimillion-selling Crazy and two albums, 2006's St Elsewhere and 2008's The Odd Couple. There was production work, for Gorillaz, the Rapture, Beck, and – in the works right now – U2. This year alone, there was Dark Night of the Soul, a collection of songs written with the late Mark Linkous of Sparklehorse, not to mention Broken Bells, a new project with Shins frontman James Mercer. But if Burton's artistic progress has been difficult to follow, it may well be because there's been a crucial piece of the puzzle missing, a piece he has been shaping since the release of The Grey Album. It is a project that has been treated with utmost secrecy – until today.

That project is Rome. Five years in the making, it's a collaboration with Italian composer Daniele Luppi, born out of the pair's love of 60s Italian film soundtracks. Recorded at Rome's Forum studios, a converted church that once played host to composers such as Ennio Morricone, Piero Umiliani and Bruno Nicolai, the record features vintage equipment and contributions from musicians who featured on spaghetti western scores such as The Good, the Bad and the Ugly, and Once Upon a Time in the West. Oh, and as if that's not enough, there are also guest spots from Jack White and Norah Jones.

Guardian.co.uk/music spoke exclusively with Danger Mouse and Daniele Luppi to hear how Rome was built.

Daniele Luppi: I've been exposed to Italian film soundtracks since my early childhood. The state-owned TV would play spaghetti westerns and the Fellini movies every weekend. I remember being just five and being, like, "Oh, it's Sunday night, time for The Good, the Bad and the Ugly". I really absorbed those sounds.

Danger Mouse: I've always watched a lot of spaghetti westerns, and I got a bit obsessed with tracking down the soundtracks. Everyone knows about Morricone, but Piero Umiliani, Bruno Nicolai, Piero Piccioni – some of these other guys had amazing stuff going on as well. Back in the early 60s, more experimental composition was looked down on, so the movies were a great vehicle to get away with doing all that.

DL: We met around 2004. Brian had just done The Grey Album and I had done a record called The Italian Story, which was basically my homage to Italian film soundtracks. I am not really a hip-hop fan, but I loved The Grey Album – Brian is able to combine the charm and beauty of old instruments with something contemporary. We had both talked about each other's work in the press, and it turned out we had a friend in common who introduced us.

DM: Daniel had just moved out to LA from Italy to do more soundtracks. He came over to my place one day and saw my collection of old Italian film music – he knows about all of this stuff, but I think he was impressed I had so much. He started helping me with some arrangements on the first Gnarls Barkley record, and we just became friends.

DL: We started to talk about this dream of doing something together, and that became Rome.

DM: First, we started writing on our own, and then played stuff to each other to find out what we liked. Then we started adding stuff – I'd add a top melody, or he'd add strings. We first went out to Italy in October 2006. In the first couple of days, Daniel made a bunch of phone calls, and we spent a day in a rented van, driving around, trying to borrow old instruments.

DL: There is no rental service for vintage instruments in Rome, so we had to go through personal contacts. We rented a vintage bass from Fabio Pignatelli, bassist for the band Goblin. There is no price for this instrument, so we went with a few bottles of wine and hoped it was the right thing to do. It was all about going with the flow.

DM: It felt a bit seedy driving around in a van with all these instruments in the back, but it definitely felt good, knowing that we were making a record that was going to be a bit different.

DL: When I made The Italian Story, I'd visited Rome and tried to track down a lot of the old musicians to see if they were alive, if they could still play. Along the way I got a lot of contacts, but the thing with Rome – and I am Italian, so I can say this – things get done, but there is no real way to plan ahead. We booked the flight, the studio, but you call musicians and say, are you free next month? And the response is, "Well, give me a call three days before …"

DM: Many of the musicians were in their 70s, but they were obviously capable. First day, they all came in and you could tell it was the first time they had been in the same room for a long time. They were hugging, some tears. But then, about two hours in, they're all yelling at each other.

DL: It was really the dream to reunite the Cantori Moderni 40 years later. It was a choir put together by Alessandro Alessandroni – think about the Sergio Leone movies, the Morricone soundtracks with those beautiful soprano melodies. Alessandroni was not only the choirmaster, but his whistle is all over those movies. It makes a sound that you could not put together with other singers.

DM: We made three trips to Rome – the first was for backing tracks, the second was mostly vocal stuff, choirs and soprano solos. It was all self-funded. I couldn't ask a label for money for something when I didn't know what it was going to be. It could have just been a hole that money disappeared into.

DL: I don't think there is a narrative to the record, but there is a feel – it is about love, death, happiness – the visceral connection of man and women. It's a dark vibe, melancholic, a little foggy.

DM: For the lead vocalists, I definitely wanted a man and a woman. The female vocal needed to be soft, not polarising. But the male needed to have a bit more angst to it. I played some of the music for Jack White when I was on tour shortly after doing the first session, just to show him what I was doing, because at the time everyone thought I was just a hip-hop guy, or whatever. He liked it, but at the time I wasn't even thinking of using him – you know, it's Jack White. But in the end, I thought, he's really into it – why not? We all understood that if it didn't work, it didn't work. But he tried it in different voices – a high voice, a low voice, and I thought, why don't we leave them all in? And it sounded great. There's a bunch of his vocals on Rose With the Broken Neck, and it doesn't always sound like him – sometimes you're like, is that Jack or not?

DL: I am very pleased with Rome – it would be bad after four years if we were not pleased. It's a small world in itself.

DM: Rome seems to have fed into everything I've done – you can hear it in a lot of Gnarls Barkley, it's all over Broken Bells too. I get a lot of offers to do film soundtracks and I've never said yes, because no one has heard this yet, and I think some people still think of me as a hip-hop producer. But this is what I would actually do, if I were to make a soundtrack. I'm really happy it's out. I just hope it's not going to take five years to do the next one.