Disco could be a heavy, unctuous perfume. There were reasons people hated it, and they weren’t all homophobic or racist. On the chart in 1977 was La Belle Epoque’s version of the German/Spanish 60s hit Black Is Black. Originally it had been a hit for another act with a tempting European name, Los Bravos. This 1966 version had been a thing of slab density, a three-note organ riff with a Charlie Watts clone’s monotone drumming keeping it simple as can be, and an unreal human voice, half-crow, telling the world “black is black, I want my baby back.” It sounded like the Stones fed through a telex precursor of Google Translate. It had been perfect – pop as monolithic simplicity. La Belle Epoque’s 1977 version added every imaginable bauble, it went “whooooo!!” on the beat. Musicians who longed to be in James Last’s orchestra played with funkless fingers behind girls who cooed unconvincing come-ons. This version of Black Is Black was a fug, like the ground floor of a department store, a dozen different perfumes hitting you at the same time, far too busy, forced fun, nauseating. The Bee Gees’ Night Fever was not that dense, liquid perfume that made you feel slightly sick. This was not the sound of too much air freshener. This was air itself. Night-time air. The city. The song, taken from the soundtrack to Saturday Night Fever, also transmitted a feeling of nervousness; there was sweetness and there was fear. The lyric to Night Fever isn’t far behind the Kingsmen’s Louie Louise or the Skids’ Into the Valley in its murk and mystery – the odd line jumps out as a waymark, the rest lure you in to the Gibbs’ world; there is a reason they never printed lyric sheets with their albums. The emotion, as ever with the Bee Gees, is conveyed by the sound of the words, the feel of that sound. The Gibbs would always be first in line to say their lyrics were “meaningless”. They really weren’t doing themselves justice. Night Fever is a great example of their almost outsider take on lyric writing. Night Fever is all love and abandon and desperation. It’s worth sweating through a 40-hour nine-to-five just for those fleeting, stolen hours when the music is everything. You share the feeling with every other boy and girl in the place. You let your inhibitions go. You are more alive than you’ve ever been. This feeling is both exhilarating and borderline terrifying. “Here I am,” sang Barry at key moments, when the music swooped downwards, away from the light and air of the verse, and suddenly it was all self-awareness. “I can’t hide!” Barry clearly understood this dynamic and used classic Gibb linguistics to push the feeling on: as the song unexpectedly takes its dramatic turn, he sings “Here I am, waiting for this moment to last. Living on the music so fast, borne on the wind, thinking it’s mine.” That’s it, the instant of delivery, the head rush, the euphoria, captured in a few words. For one week in April 1964, the Top 5 singles on the US Billboard Hot 100 were all by the Beatles. This remains the only time a single act has occupied the entire Top Five, but in March 1978, the Bee Gees gave it their best shot. The week that Night Fever went to No 1 in the US, Stayin’ Alive was at No 2 and both singles stayed put for the next five weeks; the Bee Gees became the first group, post-Beatles, to hold down the top two spots at the same time. In that first week, the Bee Gees had written or produced four songs in the Top 5 – the others were Andy Gibb’s Love Is Thicker Than Water, on its way down from No 1, and Samantha Sang’s Emotion, which would peak at No 3. Another couple of weeks later they claimed five records in the Top 10 as Yvonne Elliman’s If I Can’t Have You climbed to No 9, also on its way to No 1. The Beatles’ achievement remains singular, but the Gibbs’ moment was arguably more impressive in that none of the singles were cash-in reissues (as Twist and Shout and Please Please Me had been in 1964); also, they wrote and produced the lot. Saturday Night Fever and its soundtrack had made them the biggest group in the world. They weren’t just tapping into the zeitgeist as they had been with You Should Be Dancing two years earlier. Now the zeitgeist emanated from Criteria studios in Miami, and from the Gibb brothers themselves. Was there a reason why younger brother Andy didn’t get a song on the Saturday Night Fever soundtrack? He seemed an obvious candidate for one of the gentler romantic songs, like More Than a Woman, which had inexplicably been given to Tavares. His 1977 hit I Just Want to Be Your Everything – familiar, popular – could have slotted in as background music at any point. He must have felt shut out of the party. Maybe his brothers wanted him to stand on his own two feet. If he felt at all isolated, he must have felt a little better when Barry gave him another huge hit, his third straight US No 1, with Shadow Dancing in summer 1978. But by then his young wife Kim had gone, taken back to Australia after just a few months of marriage by her concerned parents. Stuck at No 2 behind Shadow Dancing was Gerry Rafferty’s Baker Street, another supernaturally powerful production buoying up a less than totally confident singer: “He’s got this dream about buying some land / He’s gonna give up the booze and the one night stands / And then he’ll settle down in a quiet little town and forget about everything.” Well, that would have suited Andy down to the ground. He’d try hard enough to get there. Robert Stigwood saw all four Gibb brothers as an infinite resource, a premium value asset that his RSO company owned, one that could improve the stock on any aspect of his entertainment empire. He rinsed them for material. While they could have been promoting Stayin’ Alive and ’Fever at the end of 1977, he had them in Hollywood working on his screwy idea to turn Sergeant Pepper’s Lonely Hearts Club Band into a Hollywood musical. Blonde and curly Peter Frampton, another RSO act who had been hugely successful in 76 with Frampton Comes Alive, and was still reasonably hot in 77 with I’m in You, was to be the star of the movie. It was apparent to all concerned while the movie was being edited that the Bee Gees – filmed essentially as Frampton’s backing band – had become by far the bigger name. But that didn’t help the movie which, though it cost 10 times the amount of Stigwood’s other in-production musical, Grease, was painfully bad. Still, the Gibbs had to record a bunch of Beatles songs for the soundtrack, and Robin Gibb’s crack at Abbey Road throwback track Oh Darling, which could just as easily have fitted onto the Grease score, gave them yet another US Top 20 hit. By end of 1978 all of the Gibbs, including Andy, and even most of their in-laws, were living in Miami full-time. Only Robin and wife Molly, with kids Spencer and Melissa, stayed in England. Earlier in the year they had flown over to New York for a trip to Sesame Street – Robin had recorded a song called Trash for the Sesame Street Fever album with the stipulation that his kids got to meet Cookie Monster. Released as a single in October 78, it was lyrically more of a return to his bleak 1969 solo album Robin’s Reign than an exuberant anthem: “It’s not that I don’t understand, but when the great things that I’ve planned just get wrecked eventually … trash is everything to me.” The album went gold, naturally, like everything else the Bee Gees touched in 1978. The family later flew back to New York to be presented with a gold disc by Big Bird. The Gibbs were now producing songs that could be cut to fit Beatles tributes or 50s soda shop fantasies or kiddie disco albums or contemporary teen pin-up dreams. They were a diamond mine which miraculously produced stones that needed neither cutting nor polishing. In 1978, they wrote Too Much Heaven, Tragedy and Shadow Dancin’ during a day off on the set of Sgt Pepper – probably an afternoon off, in fact, as all three songs, all future No 1s, were wrapped in about two hours. “This is a life of illusion. Wrapped up in troubles, laced with confusion.” Barry’s theme for Grease was an afterthought to the film’s real soundtrack, requested as a favour by a nervous Stigwood, a shoo-in to get the film some attention as it would be written by the hottest songwriter in the world. It turned out Grease wouldn’t need the helping hand, but Barry’s song was startling, delivered by the never-gruffer, 44-year-old Frankie Valli, one of the Bee Gees’ heroes when they had lived in Australia and possessor of the world’s most famous falsetto. He holds it back for the entirety of Grease, maybe in deference to the bearded Mancunian who had just stolen his crown. Barry must have been humbled, seeing a split screen: one screen showed him in 1978, next to Valli in the studio, coaching him through the song; the other showed boy Barry in Brisbane in 1963, holding his transistor radio to his ear listening to Valli siren-scream his way through Walk Like a Man, a direct New York forebear to the Stayin’ Alive strut. “What are we doing here?” Barry’s Grease also gave an edge to the soundtrack that songs like John Farrar’s very pretty Hopelessly Devoted to You or the yowling, cartoonish Summer Nights didn’t possess: “Only real is real.” Grease was no more an accurate depiction of the 50s than mid-70s TV show Happy Days, both being scrubbed whiter than white and exaggerating their source material until it became almost surreal. The transformation of Olivia Newton-John at the film’s end into a late 70s pin-up suggested some off-camera Back to the Future time travel sequence we hadn’t noticed – “conventionality”, as Barry might say, didn’t come into it. At the film’s end, Olivia and John Travolta drove their car upwards, toward the sky, away from the Earth, waving goodbye to both their school days and the planet. Frankie Valli’s theme – “We start the fight right now, we got to be what we feel” – was there to clear the air. The film had only been a lurid dream of the past. From now on, the end title theme suggested, let’s look forward instead of backward; there’s still work to do. The original trailer for Saturday Night Fever had featured a long shot of Travolta’s famous strut, followed by a few brief stills. It let Stayin’ Alive suggest the storyline. The trailer was wordless until an ominous voiceover: “Where do you go when the record is over?” “We’re scared of the next album” said Barry in 1978. “We’re the same desperate, worried, insecure songwriters we’ve ever been.” The bubble was yet to burst, but the Gibbs had been here before, more than once – it was only the scale that had changed. Anyway. The year 1978, the Bee Gees’ years in which they had written and produced seven American No 1 singles, ended with another knocking on the door. Too Much Heaven backed with Rest Your Love On Me, wasn’t something you could dance to, but it was sweetly irresistible. “Nobody gets too much heaven” – they knew as much, so it was best to start diversifying. Black radio and country radio picked a side each. It looked like the Bee Gees would be able to move on from disco, unharmed by fickle fashion, before the sound du jour inevitably began to fade. Bee Gees: Children of the World is published by Nine Eight Books (£22). To support the Guardian and the Observer buy a copy at guardianbookshop.com. Delivery charges may apply.