U2's fifth album The Unforgettable Fire has confirmed them as one of the world's top Rock bands. Here The Edge and Adam Clayton, along with co-producer Daniel Lanois, explain how making it was so unforgettable

Daniel Lanois reclines and contemplates the question. After having co-produced and cohabited with U2 and Brian Eno for the intense duration of time it took to create The Unforgettable Fire, their latest LP, he realises that he is the person best qualified to answer.

What constitutes the perfect Rock band?

After a sizeable wedge of time has lodged itself between statements, Lanois applies the question to U2.

"You have to have depth, strength, strangeness and consistency, the perfect balance for the Rock band. Bono has depth. The man's got a lot of depth. He's a thinker, puts a lot into his lyrics. With Larry (Mullen) you get strength because he plays from the gut, he pounds first and thinks later. With Adam (Clayton), you get strangeness. You need strangeness in a band. If everything is too profound and too strong all the time, the balance will be too much one way. So you need the guy who's going to do something a bit strange and throw everything off. Edge on the other hand gives consistency. The guy is perfectly clear all the time. Doesn't get upset, doesn't get excited really — straight down the middle and he always plays great. So if you're in trouble you bring in the Edge and you get something good."

U2 have become more a sound than a band. The sound being a chemistry of four individuals and exactly the right equipment. Even if U2 aren't the perfect Rock band, they have attained the perfect modern Rock sound. Rarely have four musicians meshed so well.

Ever since Boy emerged from the post-Punk quagmire, U2 have promised musical interest and innovation. The Edge was effectively hailed as the first New Wave guitar hero as his echo-bound guitar travelled from British sports centres to American stadiums. The rhythm section provided an intricately off-beat yet stunningly powerful backdrop and Bono's wide-ranging, emotional vocal proved the voice had returned with both bombastic and sensitive qualities intact.

The see-all, hear-all Daniel Lanois settles with the consistent Edge and the strange Adam Clayton to discuss, in one of their few interviews, the means and the ends of The Unforgettable Fire, the palatial Slane Castle in Dublin where the LP was recorded, their embracing of synthesis, their relationship with Brian Eno, their influences and the equipment that helps make manifest the anthemic celebrations of sound and hymn-like melodies that are U2's songs.

But why the divorce from Steve Lillywhite and the incongruous coupling of the perfect Rock band and the perfectly non-Rock Eno/Lanois team — a precision engineer of ambient music and a thinking man's intellectual?

Edge: "Well, I think Steve very much takes what he is given and takes the most positive things and gets the best possible sound. He also tends to have very close relationships with the band; he's very good in the studio, at understanding the band and keeping everyone loose. Really, Steve is like a catalyst but also a stabilizer. His sound is very much the sound of the band, he doesn't change it that much or get that involved in the arrangements. But none the less he's great at any session and doesn't in any way try to take over.

"But Brian, perhaps because of all the experience he's had, is far more aware of the chemistry that goes into being creative. He changed our approach to writing, our approach to doing overdubs and arranging. He opened up a whole new world to us. He brought out elements that were always there but not always out in the open.

"A good example is 4th of July. That was never designed to go on the album. In fact that was a piece of improvisation between Adam and myself. We were literally fooling around in the Ballroom, playing around on guitar and bass and Brian was in the other room where he'd set up the console and stuff. It was about 10 minutes of work and we ended up taking one two-minute section of it. Brian really likes to capture a moment. There's actually another spontaneous track that Brian captured — Elvis Presley and America — that has a completely improvised vocal. We had done the backing track and Brian had started putting all sorts of treatments on the instruments and it really began to sound like a new song. Bono was in the studio and he was so inspired by what was going on he picked up a microphone and sang that song there and then. He later wanted to go away and write a proper lyric and a more structured melody but we all wanted to keep it because it was so completely valid and showed off a quality that we always had but which had never surfaced."

Slane Castle, situated 30 miles from Dublin, on the banks of the Boyne, was responsible for the depth of sound and acoustic variety that U2 achieved on The Unforgettable Fire. Three rooms were utilised for recording. Adam: "We turned the drawing room into the control room by moving in a bunch of portable recording equipment...."

Daniel.: "It's a system from New York called the Effanel system, a Stevens machine, tape recorder. It's a very good machine. It's not quite as flexible as, say, a Studer but it's very small. That's Stevens' whole concept, the transporter is separate from the electronics and it's just the cables that connect to the tubes so one guy can haul the machine around quite easily. It all packs into its own flight cases."

Adam: "The other rooms we used were the Ballroom and the Chinese Room. The Ballroom was a huge, beautifully ornate room with enormous cathedral windows. In the Ballroom we did the very grand-sounding things like the title track, songs that needed a lot of space. We used that for the more atmospheric tracks and the Chinese Room, which was a denser-sounding rectangular room. If you hit a drum in the Ballroom you get this very long, loud reverb but in the Chinese Room you get a much shorter punchier sound. So the harder sounding tracks like Indian Summer Sky were recorded in the Chinese Room. You can hear it in that the tracks sound slightly more aggressive. More urgent sounding."

Daniel Lanois runs through an average day in the six week period the LP took to record...

"Generally a 12 hour day. We'd get up and have breakfast, and at the table we'd decide what we were going to do that day, so we'd map a plan for that day. We'd have this very large blackboard that the roadcrew would wheel into the breakfast room and this blackboard stayed with us throughout the whole project — it was basically a song list, then we'd have categories: bass, guitar, what was done, what needed to be done, what was definite. A progress chart.

"And then we'd start working after breakfast. It seems that we were eating all the time, we brought our own chef; we'd finish breakfast and then lunch would be on and it was back to the dining room. Then again back for some more work in the Chinese Room or the Ballroom. The evenings were probably the most productive time. It took us that much time to get into gear a lot of the time. Four till 10 o'clock was the best time and sometimes if we had a particularly strong idea we would work into the night. I did a few times with Adam on some bass ideas. A couple of times Brian and I snuck in downstairs and did a little bit of work, some synthesizer and some treatments.

"We had weekends off. The band would go back to Dublin and Brian and I would stay at the castle. Again we'd experiment a bit and sneak in the odd treatment here and there."

In recent years The Edge has developed something of a synthesizer bent, and the unorthodox approach he applies to the guitar in conjunction with Eno's influence has and will introduce some new elements into the U2 sound.

"I've been using the DX7 and the Yamaha CP70 piano for a while now both live and in the studio but Brian and Daniel probably contributed more on this album in the synthesizer areas. I'm playing keyboards live for the moment. That's gonna be difficult for a lot of these new songs. We're toying with the many possibilities open to us: computers, possibly, sequencer-type arrangements, even a tape off-stage — I don't know if that would hang very well — or a keyboard in addition to myself. The other alternative available, which has worked to great effect in the past, is to actually change the arrangement, which I think is quite a valid thing to do. I've never felt that we have to faithfully reproduce records live because it is such a different medium."

Despite the occasional oddities that feature in The Edge's guitar set-up, namely a 1945 Epiphone lap steel, he has found a system that he is now very comfortable with.

Edge: "I still use mainly the Strat and the Gibson Explorer, the Strat seems to be more in favour at present but it's something that fluctuates in terms of preference. The Explorer is a late 70s model and it has a very good high end with an absolute minimum of distortion. It falls equidistant between the Les Paul and the Stratocaster — warm but with bite. There's also a Washburn Festival acoustic that I use on a couple of numbers, it has a very clear tone but it's quite warm as well. I still use the Memory Man echo. It's very inexpensive but it works great and it's not at all complicated. The amps are still Voxes, similar to the ones the Beatles used. A good mid-range and powerful without being dirty. I still haven't been able to find that sound, that very clean sound in any other amp.

"I'm using very heavy strings. Heavy Superwounds as low as .011 to 0.56 heavy gauge."

Does the echo have to be set for the speed of each song?

"It's very interesting this close sound we've achieved. I think it just has to do with the environment, using all-valve microphones and a clear mix."

Edge: "Yes, I set it to the tempo of the music. And because of that echo I can then play sparser chords — physically smaller chords — and besides, Adam plays with a lot of midrange and that really fills up the sound."

Does the unorthodoxy and ostenisble eccentricity of The Edge's technique make him difficult to play with?

Adam: "I think... I quite like it, 'cos it means I have a tremendous responsibility to provide rhythm a lot of the time. It means, particularly with the sort of bass sound that I use when Edge is playing those very open-air type chords, I do have to fill in those rhythm guitar type frequencies, so that can be driving and tough. I don't have to stay with the bass drum all the time.

"I can get that midrange sound because I have two different amp setups for the two different sides of what we do. I have an Ampeg for a very mid sort of sound, boosting at around the 800 mark. Then for the more R&B type things we do I have an Alembic pre-amp going through a 750BGW into two Harpingers which have got Gauss 15" speakers and two horns in them. That is a very dry, clean sound, with a lot of bottom and a nice cutting top.

"Getting back to the interaction idea, there's a lot more interplay between me and Larry than there is with Edge and there's probably even more interplay between Edge and Larry. I tend to just stick to what I do and that gives Edge and Larry freedom to mess about with it rhythmically. Once that arrangement is established we tend to busk it on stage anyway. Like Edge was saying his echo often sets the pace, it acts as a sort of time-keeping device. It often happens that Edge and Larry put down the backing track and I add the bass later."

Where does the initial spark for a song come from?

Edge: "Well that spark can vary in many ways: sometimes it's a rhythm section thing, sometimes it may just be the bass or guitar, or Bono if he's picked up an instrument. A lot of times you can have somebody who's writing a song and then he brings it to the band, but the job isn't over because he's then got to convince the band that it is a good song. It can often be too late at that point. If the spark is strong enough everyone jumps in and creates the song."

Larry Mullen, the youngest member of the band has already become disillusioned with the press treadmill and no longer gives interviews so the onus fell on Adam to relay how Larry's style evolved.

"He never really developed into the style he plays — it was like that from the start. He has always had quite definite ideas about the rhythms he feels go with the song. I think during the Punk era when a lot of drummers played tom tom rhythms inspired him but he was always frustrated that the rhythms were very boring rhythms. He likes tom toms because they're heavy and it just seemed natural to put them in that ethnic context."

Does Adam customise any of his basses?

"No, no, it's only customised in the fact that most of the paint has chipped off it, that's what I like about it. It's a very old Precision that I use. What I like about it is that it is very unsophisticated and therefore very comfortable. It's light and easy to use, nothing is complicated. I think a bass guitar with more than two controls on it is a waste of time. You can always use external effects to create any sound you could want on the bass itself. The effects I use are an Ibanez effects unit which has... oh, compressor, overdrive, flanger, phaser which I use in various permutations. I also use an Ibanez echo unit."

How did the unconventional style evolve?

"Again like Edge and Larry it wasn't a premeditated thing and wasn't so much an evolution as an innate thing. I started off playing bass and then I got bored by that so I took up guitar for a while and began to think in terms of guitar so I suppose that was inspiration for the way I play bass. I see no barriers between bass, bass lines and melody bass lines. It's all part of the sound."

Larry's absence begins to have advantages. Edge and Adam begin to lavish praise onto him while Daniel gives the technical details to some of his finest performances to date.

Daniel: "He used all acoustic drums and two timbales and two snares, one that he calls a piccolo drum, by Ludwig, a very loud, miniature snare that measures about three inches across. He also had a Yamaha snare. So some patterns involve two snares, timbale and floor tom. A lot of the drumming sounds like a complete percussion section whereas it was Larry doing it in one take. I was very impressed with Larry."

So were the rest of the group.

Edge: "I think Larry found a new part of himself on this record. Some of the patterns he was playing were incredibly difficult, patterns that real seasoned players would have big problems with. But he really outdid himself. The strength is outstanding."

Daniel: "Something happened with Larry on this record. He really did his greatest playing. Bono's the first to admit that."

But all the same Bono's performance was very likely another personal best...

Daniel: "One of the first tracks that we did a vocal on was Promenade and I think it shocked Bono because he had this really closed presence and big sound on his voice in the headphones, and at one point I think he might have been ready to scream but when he came up to the mike it was so loud and full he didn't. A vocalist conforming to his environment. So suddenly he had this big tone in his 'phones and it caused him to be more controlled and quieter, and when a singer sings quieter, of course, you have more chance to draw on the finer qualities of the voice. If you scream, you have to get back, lower the level of the mike and it compresses it. It's like a natural form of compression which we have on this record. It's very interesting this close sound we've achieved. I think it just has to do with the environment, using all-valve microphones and a clear mix.

"The vocal mike was an all-tube Neumann. We also tried to use an AKG C-12 which is very old and has a great sound but it kept faltering so we had to abandon it. Essentially we stuck to valve mikes for everything, they have a certain warmth that you can't get out of, say, an AKG 414. The valves seemed to capture the depth and bottom of Bono's voice. I think it may have surprised him a little as he hasn't had that tone in his 'phones before. It certainly added new dimensions to his performances."

Edge: "Bono was singing through this enormous PA and Larry had two huge monitors behind him because he wasn't using headphones and the drums were spilling through the PA. It was blaringly loud. If you walked past the speakers and caught the kick drum it would knock you over. It was that kind of volume. It was very inspiring in a primitive sort of way."

Will U2's stack-climbing, massively-volumed, crowd-appeasing antics continue? Doesn't this immaturity fly in the face of what U2 are about?

The Edge is cagey.

"There will be a difference in the live shows. They will probably be less effusive. I don't know if they'll be less positive. In sections, they will be extremely uplifting, but generally speaking I think we are all a little more mature while remaining ebullient. We want people to be taken by the thought of what's happening rather than simply going wild."

The trite Led Zepplin with 'O' levels analogy becomes superceded by U2: the technical philosophers behind the swirling music.

U2 have become more a sound than a band. Think about it.