All will feature in Moroder’s forthcoming live tour, the first of his career, as will Donna Summer’s I Feel Love, which he masterminded in 1977 while rocking a porn-star tache and luxuriant perm. With its spiralling vocals and landmark synthesized bass, I Feel Love is arguably the most influential song in electronic music. It’s evergreen bangers such as that, and Summer’s majestically rude Love to Love You Baby, another co-written song, 17 minutes long and featuring 23 simulated orgasms, that prompted Nile Rodgers of Chic to call him “the man who invented dance music”. Again, it doesn’t feel like too much of an overstatement.

Sitting at a table in a private members’ club in London, Moroder smiles and shakes his head. “Well that’s not really true because Nile did exactly what I did. Chic is essential, that’s perfect disco.” Yet Rodgers isn’t the only one of Moroder’s fellow musicians to tug his forelock. In 2013 Daft Punk paid memorable tribute to the Italian on their track Giorgio by Moroder, which featured Moroder, but not as you had heard him before. Thomas Bangalter of the French duo wasn’t giving anything away, Moroder says, when he invited him to the studio. “I must say, Thomas is very secretive at what he does. Enigmatic. He is not telling.”

It turned out that Daft Punk wanted him to speak, not play. The song laid Moroder-esque keyboards over a recording of him talking about his childhood in a small town in the Dolomites (his parents ran a pensione), his early years playing German clubs in the late Sixties and early Seventies (“I would sleep in the car because I didn’t want to drive home”) and his epiphanic discovery of the Moog synthesizer.

“Call me Giorgio,” Moroder says, just as he did in the Daft Punk song, and in the same Germanic accent (he grew up speaking Italian, German and Ladin, a regional Romance dialect). He’s dressed all in black, bomber jacket, shirt and jeans, the perm replaced by a silver mane, the moustache more modest. He looks in good nick, although he asks me to sit on his right because he doesn’t hear well in his left ear (“50 years in the studio”) and he offers a fist bump instead of a handshake, having broken a finger in a fall. Across the table is Francisca Gutierrez, his wife of 29 years, the former hostess of his favourite restaurant in Los Angeles. Worth an estimated $20 million, the couple divide their time between houses in California and Moroder’s Italian home town of Ortisei. He became a father at 50 — their son, Alex, is an artist.

Gutierrez chips in occasionally to help her husband with names that escape him, which is fair enough. If you had been going for half a century, you would struggle to remember all the details. Moroder’s career has a bewildering sweep, from singing dodgy Europop in the late Sixties to his recent elevation to eulogised arena headliner. “I did the bubblegum, I did the disco, I did three Olympics,” he says (he actually did the theme songs for two Games, 1984 and 1988, plus the World Cup of 1990). “I even did a church song which is sung in southern Germany and northern Italy,” he adds. There was also Einzelgänger, an album of experimental synthesizer music. He winces. “I try not to mention that one. I could have done a little better with that.”

It’s the hits, though, that will power the forthcoming tour, as its title, Celebration of the 80s, suggests. Like Rodgers and the Hollywood composer Hans Zimmer, Moroder has realised there’s a big audience for his eclectic back catalogue, even if the original singers aren’t there. The shows will feature recorded vocals from Summer, Bowie et al, who will appear in sync on screens, with the music played by a huge live band. Moroder will be there too, although he won’t be overexerting himself.

“We have a great musical director, a great sound man,” he says. “I’m going to work hopefully not too much.” He’ll play keyboards here and there, a bit of vocoder on I Feel Love, some guitar on Cat People and he’ll sing two of his own songs: the distinctly syrupy Looky Looky from 1969 (“Oh God — my first hit, a ton of years ago”) and From Here to Eternity, a robo-disco hit in the UK in 1977.

Moroder may no longer be making what Brian Eno once described to Bowie as “the music of the future”, but he’s strikingly busy for one approaching his ninth decade. He started moonlighting as a club DJ in his sixties, and his 2015 album Déjà Vu showed that his star-pulling power is undimmed, with contributions from Britney Spears, Kylie Minogue and Sia. What’s next? “I shouldn’t say it because my wife doesn’t want me to,” he says, glancing over at Gutierrez, “but I’m going to start, probably, to write a musical.” He won’t say any more, but the thought of a West End synth extravaganza is an enticing one.

Nothing seems to faze this serene old gent. Has he ever been starstruck? “Barbra Streisand was a little . . . she’s such a legend,” says Moroder, who co-produced Streisand’s 1979 duet with Summer, No More Tears (Enough is Enough). “And maybe a little bit with Queen — what’s his name? Freddie Mercury, another giant.” He and Mercury collaborated on Love Kills, a song for the 1984 restoration of the 1927 silent film Metropolis. “There was a little tension. He was shy, difficult to communicate. But no, those were maybe the only ones.”

Which of his collaborators was most impressive? He speaks highly of Debbie Harry (“absolutely great, not only as a singer, but as a lyricist”), but “the singer which blew my head the most was . . .” A pause. “He did He Ain’t Heavy, He’s My Brother for Sylvester Stallone. What’s the name?”

“Bill Medley,” Gutierrez prompts.

“Yes, Bill Medley from the Righteous Brothers [Medley covered the Hollies’ song for Rambo III, produced by Moroder]. Oh God! He sang in one take and it was done. That’s the guy who really impressed me the most.” It was a time of extraordinary possibility. Stallone even persuaded Moroder to ask Bob Dylan to write the lyrics for another song for Rambo III. Dylan sadly demurred.

Moroder will always be most closely linked with Summer. They started working together in the mid-Seventies. Summer was fluent in German, having appeared on stage there in the musical Hair, and equally conversant in the language of lurve — hence all those orgasmic moans on Love to Love You Baby. Neil Bogart, the owner of Summer’s label, Casablanca, asked Moroder if he wanted to do a longer version. “So, I did — 17 minutes. And that song started to play in the clubs, like Studio 54.” It became one of the first great extended remixes.

Two years later came I Feel Love, Summer and Moroder’s crowning glory. “The gay community loved it,” he says, and everyone else followed suit. “I think that it was new in the way I used the [synthesizer] bassline. I think that inspired, at least that’s what they say, everybody from David Guetta to Daft Punk to the English guy who started to sing like Donna . . .” His wife chips in: “Somerville.” He nods. “Jimmy Somerville!” Somerville’s band Bronski Beat covered the song with Marc Almond in 1985.

You would have Moroder pegged as a hedonistic monster during the disco years. In a publicity shot from the period he sits by a pool in a silk dressing gown surrounded by glamorous female admirers, a bottle of champagne on the table beside him. Yet Moroder insists that he never did cocaine, as did virtually everyone else, and he wasn’t a big clubber. “No, no. I had my dance in my head.”

In the Seventies he ventured into discos only to ask DJs to test out his new tracks. “If you see people leaving the floor, it was a bad sign. If they would stay, that was good.” The irony is that he’s now in clubs all the time, having taken up DJing. It got out of hand a few years ago, he says, “but now I do more DJing in Europe because the travel to America, China or Japan, the jet lag, it’s killing me”. He favours playing his own productions, and why not? “At the end, sometimes I let them sing Call Me and I go away and have the rhythm continue.” Long may his beat go on. A Celebration of the 80s (livenation.co.uk), Symphony Hall, Birmingham, April 1; Eventim Apollo, London, April 2; Royal Concert Hall, Glasgow, April 4; 02 Apollo, Manchester, April 5