With the release of music game The Beatles: Rock Band, the world's biggest group are going to find a whole new audience. Here, Paul McCartney and Yoko Ono tell why they agreed to allow the Beatles to become interactive

There are many ways you can get to see the youthful Paul McCartney these days – YouTube, BBC documentaries, the short films that come with the Beatles' newly remastered CDs – but the best way is the Paul McCartney Soundcheck Package.

McCartney demonstrated this a few weeks ago at Fenway Park, home of the Boston Red Sox. It was 4pm, and there were about 80 people in the stadium. A few of these were lighting and sound engineers, but most were competition winners from local radio stations and fans who had paid extra for a VIP experience. McCartney smiled a lot as he played songs from Hamburg (Matchbox, Honey Don't), songs from the Cavern (All My Loving), songs from Top of the Pops (C Moon, Let 'Em In) and songs from his schooldays (Leaning on a Lamppost). The years fell away, and his performance was staggeringly good. A woman in our tiny gathering unfurled a multicoloured sign which read, "Please can you sign my Hofner?", but McCartney was far too busy having fun. Before he sang Leaning on a Lamppost, he explained that George Harrison had given him his ukulele, and before he left the stage he said: "This is a new one" as he began singing Yesterday.

When it was over he had a little chat with his band and security men, and wandered around. Catering staff said: "How ya doin', Sir Paul?" as he passed, and he said: "Good." He posed for a photograph with a young fan in a Beatles T-shirt. He came up to me and said: "I saw you were taking notes…," and I said I had been. One of my notes read: "Two TV monitors, one by microphone at front stage, other further back by piano stool. Autocues scrolling lyrics. The words I saw: He blew his mind out in a car/He didn't notice that the lights had changed."

McCartney invited me to his trailer behind the stage. His girlfriend, Nancy Shevell, was preparing iced tea in a large wine glass, and McCartney was sitting with his feet curled under him on a sofa. His dyed brown hair was not as unnerving in reality as it can appear in photographs. The trailer looked like a Middle Eastern souk – rugs on the walls, rich embroidery, sweet candles burning on low tables. I told him how much I had enjoyed the previous evening's show (the first of two nights at the same venue), and he said that he was aware he had found his groove again.

McCartney is 67, and his creativity and thumbs-up enthusiasm continue to surpass all reasonable expectations, but he learned long ago to face universal truths. Last night's concert had been a mixture of very popular music from half a century, but it was clear that the one thing his fans loved above everything else was songs by the Beatles. They whooped during a few Wings numbers (especially for the synchronised fireworks at the loud bits on Live and Let Die), but nothing approached the delight they showed for Sgt Pepper's Lonely Hearts Club Band, Hey Jude, Get Back, Let It Be and The Long and Winding Road.

Above all, his fans went nuts for Yesterday, and they will go nuts for Yesterday for ever. McCartney is happy playing the old stuff. As he explained to the Boston Globe that week, "It's like a comedian. You can tell any joke you want, but the ones that they laugh at are probably the ones you should keep in the act."

There may be several predictable reasons for McCartney's newly energised enthusiasms – the fresh girlfriend, the great reception for his tour – but there is also an unconventional one. His old band, the most important in the history of music, is about to be reborn through what was once the most reviled of art forms and the sad province of adolescent dead-enders – the videogame.

The Beatles: Rock Band is released this week amid expectation comparable to the release of The White Album. There isn't any new music, but there is a new way of experiencing it, and a new audience ready to receive it. Now a player may not only hear the youthful McCartney, but become him. And when he or she becomes bored with Paul, there's always John, George or Ringo. In this way, the adventure of pop music is being reinvented.

"We've made the Beatles music," says McCartney as he sips his tea. "It's a body of work. That's it for us – it's done. But then what happens is that somebody will come up with a suggestion…"

The suggestion for a videogame came from George Harrison's son Dhani in the winter of 2006, when he met the head of MTV on holiday in the Caribbean. MTV had just bought Harmonix, the leading music videogames company, based in Cambridge, Massachusetts.

"So we go, 'What is it? Why?'" McCartney continues. "Because one thing we don't want to do is just do naff ideas." McCartney, Ringo Starr, Olivia Harrison and Yoko Ono (known collectively and disconcertingly as "the Shareholders") began to meet people from Harmonix the following year, and McCartney remembers a meeting at Abbey Road in the spring of 2007 in which Harmonix staff demonstrated what they had done for veteran rockers Metallica.

There were "a couple of grown-ups standing looking very foolish with these little plastic guitars playing to a screen", he says. "And we're going, 'Yeah, all right… It just looks like a really bad band.' They said: 'We really can do a great one with the Beatles, and we'll show you.' So Ringo and I got a bit intrigued. They said: 'Look, the thing is, if we get it right, these things are very, very popular.' And we go, 'Yeah, well, we know, because our kids and the young people we know do it.'"

McCartney's scepticism gently lifted. "The scepticism is in order not to make a terrible mistake," he explained. "We go, 'no, no,' and we're really down on it, and they've really got to prove themselves. We won't go, 'Oh, that's nice… go on boys, you just do it.' We guard the flame a bit. But then they did come back one day and they had something. They were playing our songs, they had some visuals that were half-working, and the penny dropped. We went, 'You know what? This could be pretty cool.'"

The Beatles: Rock Band works on the same principles as other interactive music games. You insert a disc into a PlayStation 3, Xbox 360 or Wii console, you strap on a replica guitar or sit at plastic drums, and you play along to a popular song on the television screen. The song is programmed to respond to your performance: the more tunefully you sing, or the more accurately you press the buttons on the fretboard and hit the drums, the more points you get. The screen displays not only the lyrics, but a long sequence of cues to tell you when to hit or strum, with the coloured notes on the screen corresponding to buttons on your guitar. It is the digital version of the pub or campfire singalong, the 21st-century upgrade of the Victorian family parlour concert. If you play well, you get mellifluous music that sounds like your heroes. If you sing out of tune, your friends may walk out on you.

The Beatles: Rock Band takes things further. There are 45 songs to choose from, soon to be augmented by downloadable albums (in the following months you can get complete versions of Abbey Road, Sgt Pepper's and Rubber Soul). There are vocal harmonies, a complex innovation. There is very lovely animation that plays before the music begins and in the background after you start playing. There are six venues at which the songs are played (Cavern Club, Ed Sullivan Theatre, Shea Stadium, Budokan, Abbey Road and the Apple Corps Savile Row Rooftop). There is an elaborate system of gathering points to unlock rare audio and visual material from the Apple archives. And then there is the significant fact that the Beatles have never involved themselves in anything like this before. "They've done it very respectfully, and so they should," McCartney tells me. "Not just because you should respect the Beatles, but mainly because there are a lot of people out there who are going to notice if you don't."

I ask McCartney whether he's played it yet.

"I haven't, actually. I'm kind of, you know, looking forward to playing it. My excuse is, I play guitar. I was on the real record. So the idea of pushing buttons and things in time is kind of slightly intriguing for me, but it's actually more interesting to do a show like this…" He motions to the stage beyond his trailer, where his support band MGMT are playing to a swelling audience.

I wonder what John and George would have made of The Beatles: Rock Band. "I think they would have been amused," McCartney says. "I think they would have seen the point of it. For us, let's remember that the central thing is our music is getting played. That's the bottom line. I'm sure John and George would have thought, 'Hey, what a clever idea.'"

Two miles from McCartney's show, the people who made the game are talking it up with pride and amazement. Harmonix is on Massachusetts Avenue in Cambridge, just down the road from Harvard. The office sits between a pharmacy and a Get in Shape For Women studio, a series of rooms that resembles something closer to a student dorm than a company valued at hundreds of millions of dollars. (MTV bought Harmonix in 2006 for $175m, but has since paid almost $500m in additional bonuses.)

In one of the rooms, decorated with a large framed poster of the Beatles, Alex Rigopulos, the co-founder, and Paul DeGooyer, senior vice president of MTV's games division, are discussing their hopes for what may be their most lucrative game to date. "Everyone knows of the Beatles," Rigopulos says, "but there's this whole generation for whom the music isn't personal, it isn't close to them. And for that younger audience we're delivering this incredible music in the most impactful way imaginable. In a way, it's a relaunch." Rigopulos and DeGooyer are aware of their coup: now that the biggest band of all have entered the arena, it has not only created a whole new series of marketing possibilities, but has legitimised their industry. It marks the precise point at which music videogames come of age.

Harmonix began in 1995 as a concept at MIT's Media Lab. Its first clients were theme parks, and it entered the domestic market with a computer mouse that could also serve as a musical instrument on primitive games. Rock Band was only launched at the end of 2007, but already its retail sales in north America have exceeded $1bn, and gamers have downloaded more than 40 million songs for $1.99 each. As the company's co-founder Eran Egozy said recently, the delivery of rock music has just entered a new phase. There was vinyl, the cassette, the CD, digital downloads and now there is the downloadable digital interactive computer track. "It's a launching point for how we see the future of music evolving."

Harmonix has competition. Guitar Hero, made by Activision but originally developed by Harmonix, was launched in 2005 and has since sold more than 25 million copies, making it the market leader. But with the Beatles in its stable, Harmonix believes it has pulled off the ultimate coup.

Songs by the Rolling Stones and the Who were already on Rock Band, but neither of those bands were controlled by the byzantine structure that is Apple Corps Ltd, the company that has handled all of the Beatles' creative activity since 1968. But Apple has always had a canny eye for the innovative and the lucrative, and a neat way of relaunching the Beatles for each new generation (the last time it was the exhaustive Anthology project in 1995). The main problem was not the concept but the technicalities. "Apple said to us, 'We don't even want to talk about this any more unless you come up with a solution to separating out some of the earlier songs,'" DeGooyer remembers.

Rock Band requires each of the main instruments to be played in isolation, but on the Beatles early hits the drums and guitars would often be recorded on the same piece of tape. Dhani Harrison believed that the CIA would have some sort of technology to separate them, but in the end a solution was proffered by a company in Cambridge, England, called Cedar. There was also the problem of security. Apple would not permit the Beatles' master recordings to leave the studio vaults, much less travel to Boston, so once the tracks had been separated out they then had to be encrypted.

In the summer of 2007, Harmonix received five songs to play with: I Want to Hold Your Hand, Helter Skelter, Taxman, Revolution and Here Comes the Sun. The plan was for Harmonix to show how the game might work, and to conceive a rough idea of how an animated Beatles might look on screen. The songs came with instructions. "Apple gave us some guidelines to stick to," says Josh Randall, Harmonix's creative director. "They said it needs to feel analogue, it needs to feel British, and even though it's a videogame, it shouldn't feel computery. But we should also try to make something new – not just go back and rehash the old stuff."

In the end, the visual team produced a presentation based around Day Tripper, which was the first the Beatles saw of the game when they gathered at Abbey Road in summer 2008. "From each of them there were just tons and tons of ideas," says Rigopulos. "They said: 'Oh, you could do this, you could do that, you could do this…'"

"We did get very hands-on," McCartney says. "We said: 'Show us everything – how does it work?' They said: 'If you attain a degree of efficiency you'll then get points, and your prize will be trivia facts about the Beatles.' I said: 'Oh great – show us them.' So they showed me one and I went, 'Oh, that's wrong.' It was the first one up.

"Some things you just do 'em: somebody's doing a book or something – we'll help them, but it's not our responsibility. But this is going to go out in our name, so we really have to be careful."

According to Rigopulos, McCartney asked a lot of pointed questions. "He wasn't aloof at all. He really did care about accuracy. There were some ideas we had about mixing and matching times and places that intentionally disregarded historical accuracy, and he put his stake in the ground. We said: 'Maybe the rooftop concert can have songs performed that actually you guys didn't perform on the rooftop.' And he said: 'No. There are some things we can play with, but some aspects of the design we should be true to.'"

In the game, the Beatles are animated in imaginative ways. Given the band's history with Yellow Submarine, this will not be unfamiliar territory for the older player, but it caused a lot of heartache at Harmonix. McCartney is a keen fan of modern animation, not least because he watches films with his grandchildren and the five-year-old daughter he shares with Heather Mills. He felt that the early work was not hugely impressive.

"We said: 'Look, the eyes don't work.' They said: 'No, eyes are very hard to do….' Then: 'Wait a minute, John's too wooden…' I started to say, 'Look, Shrek's good. There's this great thing, Arthur and the Invisibles, the Luc Besson film.' So I started to give them things to aim at."

Josh Randall says that all the Beatles and their wives were heavily involved. Talking on the phone from Henley-on-Thames, Olivia Harrison will tell me later that she thought there was a problem with the proportions in early drawings of George's face. "I started to look at photos to see where they went wrong. I thought they could capture those eyes, and get that little bit of a crooked smile." She had played the game with Dhani in LA and was eager to have another go in private. "It makes you appreciate music a little deeper. We don't have a band, but the music exists, and I don't see any harm in letting people have another way of experiencing it."

It was Yoko Ono who apparently caused the most problems with the game's designers. Alex Rigopulos remembers one visit to their office during which Ono reminded them how windy the rooftop concert was, necessitating changes to the band's hair. There were other corrections: "She would tell our animation guys how John would approach the mic, how heavy his eyes would be, giving them quite a hard time. But at the end she said to them, 'It's OK – I'm an artist too.'"

From Tokyo, by email, Yoko later responds to my questions. "We, especially Olivia and I, were very caring about how the images of the Beatles were represented, as well as the music," she says. "The Harmonix people were keen to involve us. I think they were really happy that we wanted to integrate ourselves so much into the project."

She hasn't had time to play the game, but promises to "explore it properly" when she finishes promoting her new album. "As a parent myself, I am very aware of the highly educational aspect of this game," she says. "It will inspire and encourage the young generation to be intimately involved in music making. You can't ask for more. It will be another musical revolution created by the Beatles to make our planet a planet of music."

The last key figure in the making of the game was Giles Martin, the son of George Martin. His remixing of the Beatles hits for the Love project (the Beatles collaboration with Cirque du Soleil in Las Vegas) had earned him the trust of the band, and he acted as the middleman between Apple and Harmonix, helping to select tracks for the game and create new precise endings for songs that had previously faded out. He too was initially suspicious of the idea. "I was thinking, 'Am I making a Beatles Zippo lighter or a Beatles plastic tray?' I was snooty about it at first – 'Oh God, we're just making a game.' There's part of me, being a musician, that wants to say, 'Why don't you go and play a proper guitar and not play a plastic one?' But what I do like about it is that it makes us listen to the music again and again, in the way that we used to when we bought albums. As opposed to having 3,000 songs on your iPod which you flick through with obsessive button pressing. These days we do hear a lot of music, but we don't actually listen to it very often."

Giles Martin told me he was surprised, when he tried to play I Want to Hold Your Hand, at just how complex the bass line was. I knew what he meant. At the end of my first day at Harmonix, I entered the company's Star Chamber, where the games are tested. It is also the room where staff come to relax after a hard day's struggle with Ringo's cymbal crashes and George's eyelids.

Shortly before I was joined by publicity and other staff for a "concert", I picked up a replica of McCartney's Hofner bass propped up on a leather sofa. This had been designed on a slightly reduced scale by Matthew Reineck, who also makes real guitars. The Hofner and the scaled-down models of Lennon's Rickenbacker, Harrison's Gretsch and Ringo's Ludwig drums were plastic, but they felt OK in the hand. Reineck explained that McCartney's bass had been made with great attention to detail (Hofner had supplied a special sample of the wood grain), but there were also variations. Unlike the original, the guitar was designed for a right-handed player, and it came with a "whammy bar" to enable nice sustain effects and ensure "backwards compatibility" with other Rock Band games. "McCartney reviewed it halfway through the design process," Reineck said, "and he didn't have an issue with it." The Hofner will come bundled in a big box with Ringo's drums and a microphone with stand, and will retail for £180. The Rickenbacker and the Gretsch will each cost £90, while the game just on its own (requiring the use of older Rock Band instruments) will cost either £40 or £50 depending on the console.

As Reineck was talking, various people arrived in the room and strapped on their wireless guitars. One of them inserted a disk in the machine, and apologised for a slight technical glitch: the Rickenbacker had run out of batteries, a dilemma the Fab Four had rarely encountered. I was surprised how much visual information is displayed on the screen all at once – it was like a musical satnav. It helps if you have a big TV; in fact, it is hard to see how the game could have existed before we all went mad for massive flat screens. I was asked what song I fancied and I plumped for Sgt Pepper's, but as a singer. One man took pity on me and set the difficulty level to Easy. (The game has five levels: Easy, Medium, Hard, Expert and No Fail, the latter a sort of training-wheels option to ensure the cloth-eared are not discouraged.) The music began, that familiar chugging. I began singing – that familiar awful sound. But I was keen, and it was less fraught than regular karaoke (you don't have to be drunk for a start), and I became a part of the act I'd known for all these years.

I appeared to get the right words at the right time, and when the song ended (this took a while, as of course it segued into With a Little Help From My Friends) the screen showed I had scored 99 out of 100. Vaguely preposterous, but I had made my small contribution to unlocking a rare photograph of the Beatles in the studio with information about the first time they all sported moustaches, and once I had enough of these I would unlock some rare audio of the Beatles goading each other about messing up an intro.

Glowing with success, I had a shot at Get Back. Not so good; only 97%; the rare photograph of George Harrison playing sitar on Magical Mystery Tour would have to wait. Overall, I wasn't so sure this was a good hobby for a grown man. The future of music? Others seemed to think so.

I asked Olivia Harrison what George would have made of it. "I hate to say, but I know I'm his biggest fan and biggest critic, and I'm happy with it. I think they did a great job, and if I didn't like it I would feel very uncomfortable."

Yoko told me: "People are always asking me what John would have thought of our new technology – email being our standard way of communication now etc. He would have loved it all. He was always for new ideas to give inspiration and encouragement to the world. He would have been excited about the Rock Band concept, and very happy with how the music and the visuals of the Beatles were represented."

Given the likely success of Rock Band and the remastered catalogue, Marty Bandier, the chief executive of Sony/ATV publishing, said: "The fourth quarter will belong to the Beatles."

Backstage at Fenway Park, Paul McCartney is 90 minutes away from another night on stage. He is explaining how the Beatles got their look.

"When I was a kid, I went with my parents and my brother to Butlins Holiday Camp at Pwllheli. I had a vision… what do you call it? An epiphany. I was by the swimming pool, and we were such a funny family, a little bit Alan Bennett. From a door in one of the buildings, I see four guys walk out in a line. They were all dressed the same. They all had grey crew-neck sweaters, tartan twat hats (as we used to call them, like the Kangols everyone wears now), tartan shorts, and a rolled white towel under their arm. They just walked, and I thought, 'Holy shit!' They were in the talent show. Then I went to see them in the talent show, and they wore grey zoot suits, and they were from Gateshead, and they won. And I totally remember that. So when we came to be the Beatles, I said: 'You know what?' and I told everyone about this epiphany. And so we ended up in suits and we all wore the same."

This was an unfamiliar yarn, and I was aware that McCartney had a reputation for reinterpreting history. Or perhaps his memory had become sharper as he aged. I said that I had always thought the look was Brian Epstein's idea. He said: "I don't think it was." He explained that the suits may have been Epstein's thing, as it was the only way they could get the better-paid gigs, but McCartney thought the idea of all looking the same was probably his own. "When we showed up at a gig, we would come in like this [regular street clothes], and then we'd get the boots and the suits, and suddenly we were the four-headed monster, and it was a very exciting feeling. We'd look at each other – wow! And we'd become more than the sum of the parts. We'd become the Beatles."

The show that night was terrific. Thirty-five thousand people had an epiphany of their own. The concert also marked another Beatles milestone, for as McCartney sang Got to Get You Into My Life, from 1966, the vast screen behind him showed an animated film of the Beatles from 2009. "The pictures you saw there are from this new Beatles Rock Band thing," he said. His fans clapped and whooped, because they had been presented with a new opportunity, the ability to recreate tonight's event at home. Batteries required, unsurpassed creative genius optional.

Yesterday's sound today

"The idea is to make the Beatles sound as good as they can," says Allan Rouse, talking at Abbey Road. He is the co-ordinator in charge of the digital remastering of the Beatles' back catalogue. This means that the Fabs' 12 albums, plus Magical Mystery Tour, which became part of the core catalogue when the first Beatles CDs were released in 1987, now boast a brighter, fuller sound. Some bad edits, dropouts and vocal pops are gone; but the odd cough, John muttering "fucking hell" during Hey Jude - this sort of thing remains. "De-noising" - removing analogue tape hiss - has only been applied to five of a total of 525 minutes worth of music. The release of the remastered CDs coincides with the arrival of Rock Band - "because," says Rouse, "the Beatles are for everyone, not just for people in the past." Caspar Llewellyn Smith

Games without frontiers

The next wave of music-themed computer games due in time for Christmas includes:

DJ Hero

Endorsed by Eminem and Jay-Z, right, this has you scratching and mixing tunes by the likes of Bowie and the Beastie Boys. Released on 27 October, it will retail at around £90, including turntable-shaped controller.

Rock Band Network

Will allow any artist, whether established or up and coming, to create their own music into tracks for the Rock Band game, and make money from it. Once approved, they'll be sold on XBox Live. Launches soon - check out http://creators.rockband.com.

We Sing

EMI, Warners and Universal are opening up their back catalogues to this Wii-based competitor to Sony's SingStar. Allows four people to sing along to the likes of Lily Allen.

The Beatles and iTunes

It's one of the great unanswered questions of pop: why no Beatles on iTunes?

"We've been keen to do this for a while," Paul McCartney told OMM. "I met Guy Hands on a plane once. His crew bought EMI. I refer to them as Terracotta but I believe it's Terra Firma. I said: 'What is the problem? I want to do it, we all want to do it.' And he explained that in the deal that we want, they feel exposed. If [digitised Beatles music] gets out, if one employee decides to take it home and wap it on to the internet, we would have the right to say, 'Now you recompense us for that.' And they're scared of that."

There may be other reasons. George Harrison's son Dhani said recently that there is a disagreement over the pricing of Beatles songs; there are hints too that the band have considered setting up their own download store. The official response from EMI is: "We would love to see the Beatles' music on sale in digital stores." Simon Garfield

The Beatles: Rock Band and the Beatles' remastered albums are out on 9 September.