Look, let's be upfront about this.

Dead Rat Orchestra is, quite clearly, a terrible name for a band. Even the band members admit as much. "I normally say it now and cringe as I say it," Dead Rat Orchestree Nathan Mann concedes when I raise the interface of chosen moniker and rubbish quotient. "And I have to clarify that we're not 15 and it's not black metal. But strangely Spanish people think it's a fantastic name and North Americans tend to think it's brilliant."

Well, the Spaniards and North Americans are wrong. But not to worry. If it's clear that the orchestra hasn't wasted a lot of energy on nomenclature (the name was inherited from a previous band featuring Mann's Orchestra band mate Robin Alderton) that just leaves all the more to put into their music.

The orchestra's first album, The Guga Hunters Of Ness, is, frankly, a delight; a ramshackle, salt-sprayed, water-spotted, smoke-infused collection of tunes that are steeped in Hebridean influences yet reimagined and reinvigorated with a giddy originality. And then some.

It's the first album the orchestra has made in its 10-year existence. Regularly tagged "avant-folkies", in the past you'd have found them making site-specific music in old churchs and abandoned spaces. They once spent five days in an abattoir in Madrid constructing a giant harp out of fishing wire which they hung from the lighting rig and tuned to the sound of the space. That's what you get when you combine three musicians with a fine arts background (they've all been immersed in sound art) with a love of old music. The result is a trio –I haven't mentioned third member Daniel Merrill yet –who even make music out of cutting up logs. (They do. You can Google them doing it on YouTube). To be fair, they are big on fiddle and harmonium too.

In a sense, then, The Guga Hunters Of Ness is almost conventional by Dead Rat Orchestra standards. Originally the soundtrack for a BBC documentary about the traditional annual trip 10 men from Ness make to harvest the gugas – young gannets – on Sula Sgeir, it's been completely remixed and extended for its album release. The soundtrack grew out of a meeting with the documentary's director, Mike Day, at a Dead Rat Orchestra gig.

"Mike was at a concert of ours in London," explains Mann, "and afterwards he came up and said 'the last song you played, that's the soundtrack to my next film'." It wasn't in the end. Instead the DRO (if ELO is good enough for the Electric Light Orchestra ...) came up with something new for the film. Or a mix of new and old.

Before they started, the band decamped to the Vaughn Williams Memorial Library in Cecil Sharp House in London to steep themselves in Hebridean folk song in the library's archive. There they listened to BBC tapes of Hebridean women singing while they stretched wool. "We were expecting really dour, demure music but we discovered the most lively and vibrant sound. It almost sounds like polyphonic African singing and it was a joy."

Suitably inspired, they set to work. "The traditional songs acted as seeds for the composition. Sometimes you'd be hard-pressed to find where these things ended up. But we would hear a certain sentiment within it. We really got under the skin of this and it's something we've invested so much in and that we're all very proud of."

Of course they wouldn't be the Dead Rat Orchestra if they didn't make it interesting for themselves. So for the recording they decamped from their Colchester base to a decommissioned lighthouse ship on a river in Essex (meaning the acoustics changed with the tide), where they renewed the old and added the past to the present. On the track Salt Slide they embed director Mike Day's field recordings of the Ness Choir in an ambient liquid drone. "For us it was quite important to include something of the voices of the people there, and they have a very unique way of singing," says Mann.

The album, and the accompanying tour, is a new chapter in the DRO's decade-long existence. Mann was 20 when he joined the Dead Rat Orchestra and he can't now imagine life without it. "It is my musical background. We've grown together and developed together. Now we've all got independent projects which feed off and feed back into the Dead Rat Orchestra. It is a long-term project."

The other week Mann and his bandmate Daniel Merrill composed a piece for the London Contemporary Orchestra. Mann has also recently been appointed Musician in Residence at the Pitt Rivers Museum in Oxford, a role that will last 18 months, though what it will entail he's not willing to reveal yet. "I do have some ideas and I hope it will involve pigeons. That's all I'll say."

It all points to the breadth and depth of their musical interests. "We're very open. Our palette is very broad," Mann suggests. "But it's not something we've set out to do. It's just very natural within us. It's never a contrivance, like 'let's see how weird we can get'."

Once you hear them, that rings true. Their sound is rich and strange. The last thing they are is some contrived notion of weird. They're better than that. They're better than their name too.

The Guga Hunters Of Ness is out now on the Critical Heights label. The Dead Rat Orchestra play the Old Hairdressers, Glasgow on July 18.