I am about to meet Alex Rose, the man who plays the synthesiser in Minus the Bear, and I am nervous for a number of reasons. At twenty past five on a Friday evening hung bright with heavy sun, Villiers Street is seething with post-work drinkers still dressed sharp for their City jobs, getting gently lit while determined tourists with Olympic hangovers push on up to the Strand or Nelson's Column, and unkempt stubbly chefs in sauce-splattered Crocs sneak smokes down steamy alleys. I have never been to Heaven. If I've memorised the map right, I should be standing on top of it. Hot sweat is seeping greasily through the back of my own work shirt. It is a bad day to be wearing wool socks.

So here's Reason Number Two. In 2005 an album called Menos El Oso was the background noise to a summer without compare, united friends' warring tastes encompassing Zeppelin, Chimaira and Infected Mushroom, encouraged a nascent guitar style. Two years after this, another album called Planet of Ice kept me perversely warm, stranded away from home among what I perceived as throngs of casual businessmen on matters of the heart. Half a decade later again and I'm stood outside Charing Cross station, overheating and squinting and confused, my phone jammed to my ear. After some awkwardness born of bad signal and fresh acquaintance, I am spotted and ushered inside Heaven (it was down the shopping arcade. Who'd'a thunk it.) by Joe, the interminably patient PR guy who's set this whole thing up. Inside I dawdle around front of house with another writer, nervy and mouse-mannerismed, who doesn't say much, and we watch Minus the Bear soundcheck the tropic-textured 'Toska' from new record Infinity Overhead. Soundcheck over, I am led upstairs by Joe, clutching my notebook in clammy fingers, and fumble through a conversation about work and the weather with Big Scary Monsters head honcho Kev, who's putting out Infinity over here. Alex ambles over, tall, smiling, chilled to the point of stoned. He has on some kind of badass crystal ring shaped like a skull (I think). In hindsight, I wish I'd asked him about that. We split and take up residence on a sofa in the corner of the production office.

I don't want to piss off anyone who might be jetlagged. Test the water. Did you just get in today? "Nah," says Alex, tired nonetheless, "we flew in Wednesday…drove to Pukkelpop… drove back after our set Thursday, and kinda woke up a couple hours later in London." Belgium ain't so different a timezone. We're fine.

Our first points of experience with Minus the Bear are usually honey-voiced frontman Jake Snider and super-tech Botch grad Dave Knudson, certainly in terms of recorded presence, so I decide to ask Alex about himself. What's his remit as a keyboardist in Minus the Bear? How involved does he get in songwriting on that front? "It's fairly democratic," he replies. "A lot of the songs start with a Dave guitar riff, and then he and Erin (Tate, drums) work out an arrangement and we'll all come in and add our opinions. In general, I write all my own parts but also contribute to arrangements. It's fairly free reign as far as what I can do." I think I read Jake as saying a while back that synth isn't your first instrument… "No, saxophone was my instrument for a while and I play that a little bit on the new record (that's Alex going all 'Baker Street' over the closing moments of 'Lonely Gun'). I did guitar and bass and drums in various bands kinda depending. I was Minus the Bear's sound guy before I joined, and then Matt Bayles quit to focus on production and I kinda just raised my hand and was like 'I'll do that!'"

For me, Alex's musical history dovetails with the bipolarity of his parts. One thing I've noticed about your playing in Minus the Bear, I say, is that it's quite schizophrenic. One minute you're doing this squelchy synth thing and then you're pulling out a Rhodes or something. Is that a conscious default thing or do you think that Minus the Bear lends itself to that kind of switching up? "I think Minus the Bear does lend itself…" Alex considers, and finds a thread. "There was an early recording on Planet Of Ice where I hadn't added any high-energy synth parts, and Matt was like 'I think this song might need some of that somewhere', so I guess I was kind of following in the footsteps of the song a little bit. I really like Rhodes sounds and stuff, but sometimes you really wanna freak 'em out!" Yeah, 'cause I noticed in 'Diamond Lightning' one minute… "YES! That's exactly what I was thinking!" …you're going like (I make a wobbling, squishy noise), and then you're pulling out this organic piano sound… "…I like both of those sounds a lot." Reason Number Three. I am bad at talking to people.

So I change tack. Something more sensible. Speaking of Matt, how is it working with your predecessor behind the desk? "It's interesting." Interesting. "I was a little freaked out on Planet of Ice, but since we did the Acoustics EP together, I know what to expect, and he's not overbearing in any way, he's very encouraging." Go on. "He's always respected me as a musician…which isn't to say we don't butt heads, because we do! But as far as a keyboard thing, it's very respectful." You worked with Joe Chiccarelli for OMNI, as opposed to Matt. Why so? "I think on OMNI we wanted to try something new, get out of our comfort zone, have that experience of saying like 'what can someone like that bring to us?' and I think it was a great experience to have." So why the reversion to Matt? "I think we just knew the process (with Matt) so well, it was like stepping into your old shoes, going 'this group of six people knows how to make a Minus the Bear record, let's do this!'"

Infinity Overhead is certainly a Minus the Bear record, in its warping of the sound of its predecessors. Just as Highly Refined Pirates' fiddly melancholy begat the more streamlined and sparkling Menos, and Planet of Ice's frozen proggy expanse thawed into the swirling decadence of OMNI, OMNI has begotten Infinity Overhead, a record that swaps its sire's carnality for crunch while retaining its swaggering songwriting. "From the get-go," explains Alex, "Dave wanted to do more aggressive guitar sounds. Matt has this organic thing to his sound, and we kind of wanted to go dirtier than before." The pigeonhole-happy press up to this point has intimated as much. Do you agree with Infinity being touted as 'guitar-laden', 'heavy', so forth? "I do agree with that," says Alex, "but I disagree with OMNI being called a very keyboard based record…I guess I get it, but I don't think that it's 'that's keyboards and this is guitar'." So what prompted the shift in sound? "What we wanted to go for on OMNI" Alex continues, "is not necessarily what it turned into. While it has a lot of keyboard moments and some electronic-sounding stuff, but…like on 'Animal Backwards' Erin played all the drums. I think it wasn't as electronic as something like the Beer Commercials EP." I'm kind of thrown at first, I thought we were talking about Infinity Overhead, but there's a point to all this. "I don't wanna say that the shift in sound between OMNI and Infinity Overhead was because of fan response," Alex goes on, referencing a reception which flickered from haughty to indifferent to disappointed and even acerbic, "but it's kind of interesting because…we make OMNI and people say it's this thing, and we're like 'really? OK, so let's do a fucking balls-out rock record.'"

There is a point to all this for me too. Here's Reason Number One, and where I've been a yellowbellied no-guts out and out coward. I've given it time and a kind ear, and here's not to say why, but at the time of both interview and writing, I do not like Infinity Overhead. So framing it in my head as a reactionary experiment is comforting, although I'm sure that this isn't what Alex meant. 'Lonely Gun' is my main sore point, its thrusting wah-wah and macho rhythms eliciting instant emotional shutoff, so far removed are they from the Aurora Borealis of twinkling pulloffs that once floated and flurried about my headspace. But I do not say any of this to Alex. I stutter out

"For me it was almost…shocking in a way, because it's very, almost like cock rock (I go 'waoogh…waoogh waoogh WAOOGH' in an impression of the song's central riff), it was weird to hear Minus the Bear going for that…"

He laughs. "It's weird", Alex says, grinning, "to hear it out of sequence. I took a couple of months off from the album, and the song's very different second to last on the record from on its own, I think we freaked some people out." You did that. He goes on. "I would like to think that in sequence it makes sense, but it is an eclectic, chaotic group of sounds if you sample them separately." I ask Alex what the band were listening to around the time of writing. "Aaahh…good question!" He thinks, looking at the ceiling. "I was listening to a lot of electronic stuff…Caribou, Four Tet, SBTRKT...." We have a good jaw about how much we both like last year's SBTRKT record, but hearing this response, I realise I've been waiting for him to say that Mötley Crüe were in heavy rotation on the Minus stereo. "Erin was listening to a lot of Led Zeppelin", he offers. So what's fan response been like so far? "'Diamond Lightning' has had a really great response. I can't wait for people to hear that with 'Toska' coming after it." And this makes sense, 'Diamond Lightning' is Infinity Overhead's premium cut, a widescreen glow that casts its light somewhere around the heels of 'I'm Totally Not Down With Rob's Alien', just about lifting us out of ourselves and up and into the warm starry night as Minus the Bear's best songs manage with ease. "I think those two are what I consider the centrepiece of the album in a way," Alex goes on, "as far as achievement or what we're excited about goes." It is nice to hear him say this. You can make up your own mind about Infinity Overhead, which came out on the 28th.