Imagine for a moment that Postcard Records had never existed; that label boss Alan Horne never met Edwyn Collins; that Orange Juice never got beyond Bearsden Academy; that Roddy Frame never got out of East Kilbride.

Imagine all of this and then ask what difference would it have made?

Possibly quite a lot. Some fine records for a start. But more than that, much more than that, would Scotland have managed to be so central to British pop in the 1980s? Would indie music have developed the way it did? And, the biggest question of all, would Glasgow matter to anyone beyond the G40 postcode?

Why ask in the first place? Well, the origin of this pop culture counterfactual was inspired by the publication of a new book, Simply Thrilled: The Preposterous Story Of Postcard Records by music writer Simon Goddard. It's an arch, concise book about an arch, short-lived record label and the people who made it tick, and it raises another question: why should we still care? Why does a record label now over 30 years old that only managed to put out 13 records from four different bands (Orange Juice, Aztec Camera, Josef K and token Aussies The Go-Betweens) inspire books like this? What, in short, is the legacy of Postcard Records?

Simon Goddard was just a kid when Alan Horne decided to set up the label. He had no first-hand knowledge of what it was. By the time he was an indie kid, Orange Juice were just a band he'd seen on Top Of The Pops performing Rip It Up. It was only when he got to hear the reissue of the band's original Postcard recordings in the 1990s that Postcard began to make any sense to him. "I suddenly realised all the crap indie stuff I'd listened to in the 1980s was basically a rip-off of Postcard. It's almost like I'd grown up as a teenager listening to Shaking Stevens and suddenly here was Elvis Presley," says Goddard.

Douglas McIntyre, the man behind the Creeping Bent label and more recently a key figure in the We Can Still Picnic collective, is a little older than Goddard and was Presleyed by Postcard back in the day. "I guess I was the perfect age for Postcard. I was in my late teens when it was happening. I'd been really massively inspired by punk and particularly the side of punk which, I guess, inspired Postcard - the Subway Sect, Buzzcocks, Alternative TV. So when Postcard first started, it really did feel like it was the first good thing that had ever happened in Scotland to my ears in terms of being directly influenced by punk."

It helped that in their interviews in the music press Orange Juice namedropped all the musicians he loved who were frowned upon by his punk mates. "I wasn't meant to be into hippy Neil Young and disco's Chic. It made me think 'Oh, these guys are on the same trip I'm on'."

Postcard offered something fresh, something bright, something funny (with the Louis Wain images of cats on the covers, there was to be none of the cold minimalism of Joy Division and Factory Records here). Something brave too. "What was it like in 1979 to get on stage looking like Edwyn Collins and singing 'step we gaily on we go' in Glasgow?" wonders Goddard.

In a sense, Goddard suggests, Postcard effectively invented what would become indie in the 1980s. You can see its influence in everything from Cherry Red Records to the C86 movement, which began with an NME compilation that included the likes of The Shop Assistants, The Pastels and an early version of Primal Scream.

"In 1980, indie music didn't exist as a concept," he says. "In a way Postcard was the Book of Genesis of what would become indie music in the 1980s. I know Alan Horne wouldn't be happy saying 'This is my legacy' about a lot of the bands Postcard inspired, but take a band like The Wedding Present - who were very successful, signed to RCA, had a major contract. Pretty much their chord changes and lovelorn lyrics, you could argue, were entirely based on Orange Juice."

"I think the C86 scene wasn't the bastard child," adds McIntyre. "It was almost the bastard little brother. And that's fair enough. You are always influenced by those a couple of years before you. It's a natural thing. And there was a lot of great stuff that came out of C86. It's easily derided as a genre but there was a lot of good stuff involved. But obviously all the Postcard gang hated it."

Perhaps that's because the likes of Talulah Gosh had none of the same ambition of Horne and Collins. "Alan and Edwyn weren't saying 'Let's release these wee records and get on John Peel and get in the indie chart," points out Goddard. "Naively but genuinely, they thought of it as pop music and they wanted to be in the Top 10. They were very populist in their thinking.

"A lot of the bands who have cited Postcard as an influence have a slightly closet mentality, are quite happy to be a cult little band. Postcard wasn't about being small and indie. It wasn't about this cottage industry of underachievers, which is sometimes something indie became later on. Alan would say 'We're going to find Paul McCartney and ask him to produce Orange Juice.' Even though that was a wheeze, the fact is they were thinking that big."

Unfortunately, their distributor Rough Trade were in no position to deliver the Top 40 placings the label hoped for and eventually the bands all moved on to major labels. And maybe it could never have happened for Postcard anyway, given their personalities. As McIntyre points out: "Alan was never a people person".

Then again, Goddard suggests, if Horne had been successful in licensing Laurie Anderson's Oh Superman things may have been different. But in August 1981 Postcard released its last single - Aztec Camera's Mattress Of Wire - some 21 months after the first (Orange Juice's Felicity) and, but for a slight return in the 1990s, Postcard Records was done.

Frame and Collins kept on making records, of course. In a sense their work is the obvious legacy of Postcard. More than that, though, the idea lived on. It was a desire to recreate the excitement he felt as a fan that inspired McIntyre to set up the Creeping Bent label in 1994 which has since released records from the likes of Adventures In Stereo, the Nectarine No 9, Bill Wells and Isobel Campbell and even never-quite-made-it-to-vinyl Postcard band The Jazzateers.

"We're doing unreleased Postcard stuff. There's just a real interest from a young audience. It's not just people who are 50 now," McIntyre says.

And McIntyre's latest venture, We Can Still Picnic, also has echoes of the Postcard model, he suggests. "We've got Casual Sex and a band called POST, and they are definitely filtering a lot of the campness and attitudes that were around Postcard and have synthesised it into something new the way Postcard synthesised a lot of the ideas that Warhol and the Factory had.

"There are parallels. The thing about Postcard was they were determined to achieve attention. They weren't going to sit back and be hip on Byres Road for two minutes. No, they were going to go out there, go to London and get attention from the music press. In the same way Casual Sex are going over to America and the New York Times are writing about them. They're doing all this on We Can Still Picnic. There's no money behind it. There's no big label. But they've toured America with Franz Ferdinand."

Maybe then the attitude of Postcard - the energy, chutzpah and, as Goddard says, "the balls" that made Horne send Elton John a letter to say "give us some money for our band, you're not very good any more" - can still be found at large and alive in the Scottish music scene.

And maybe, just maybe there wouldn't be a music scene at all without Postcard. After all, before Horne and Collins, Glasgow didn't mean very much in pop culture terms. It meant Maggie Bell, it meant blues rock. It meant, on a good day, Billy Connolly. Orange Juice with their racoon hats and camp humour changed the image of the city and in the process turned it into a national music city that it hadn't been before. "You'd had Scottish pop stars before, from Lulu to Kelly Marie. But it was through Postcard and the hype it created in the London music press that suddenly A&R men began to take Glasgow seriously as a place to find bands. Postcard and Orange Juice were the ones that shook the bottle."

And so maybe everyone from Altered Images to Belle And Sebastian to Glasvegas owe a debt to Alan and Edwyn. Postcard, along with Bill Forsyth and Alasdair Gray, helped put Glasgow on the cultural map back at the start of the 1980s and helped reinvent what Glasgow might be. A smarter, funnier, less macho, more beautiful place. In the end, then, we are all Postcard's children.

Simply Thrilled by Simon Goddard is published by Ebury Press, priced £16.99. For more about the Creeping Bent Organisation and We Can Still Picnic, go to www.creepingbent.net and www.facebook.com/wecanstillpicnic