Collecting: The sweet sound of 33 revolutions per minute

"People don't really start a vinyl collection. They just realise they have one," says John Stanley, author of Miller's Collecting Vinyl, the authority on the subject. "They develop an interest in a particular band or genre, or even something outside music like film or soap operas or a comedian, and they end up with a vinyl collection connected to that."

If you are over 30, it's likely you are a vinyl collector without knowing it. According to research by NatWest FastPay, a service that lets you send money to anyone in the UK by email or mobile phone, we are hoarding £3.5bn worth of "old stuff" - 9 per cent of which is old vinyl.

You probably have at least a few records in the back of a cupboard, and even if they are by obscure bands, they could be worth something.

Quite often, the more obscure the record, the more valuable it is. "Perry Como sold millions in his lifetime," says Mr Stanley, "and still has a loyal fan base, but one of his records in perfect condition will only fetch about £5. Whereas the records of one band I managed back when I was at university are worth £60 each. Some members of that group went on to form another band, which is now considered a forerunner of punk, so they've become collectable for that reason and because they sold so few."

On the whole, records that sold millions are likely to fetch next to nothing unless they are a special edition or obviously a first pressing. While you can tell with books which are first editions - because it is printed on the flyleaf - records carry no such mark.

The only way aficionados can tell a record is a first pressing is by minute changes in the covers or on the disc itself. For example, the Rolling Stones LP Big Hits (Hightide and Green Grass) is worth £40 if it has five lines of small text on the cover and £8,000 if it only has two lines of text. Buddy Holly's EP Listen to Me is £40 if he is wearing glasses and £350 without.

The most likely fans to own six-figure-value collections, unknowingly, are journalists or DJs who have stacks of review copies and promotional material.

Kevin Greening, a former presenter of the Radio 1 Breakfast Show, has thousands of vinyl records thanks to enthusiastic record pluggers. "What disappoints me," he says, "is that records you really love or that mean a lot to you are always the ones worth 20p. I should be pleased because it means I'll never be tempted to sell them, but it still annoys me."

Another unique aspect of vinyl is the extraordinary range of categories within which people collect: there are, for example, 23 types of jazz, 20 of rock, 21 of pop and more than 50 of punk. A recent big favourite is easy listening, which incorporates mood music, lift music and 1950s crooners.

"Some records become more valuable because you have different groups of people vying for them," explains Mr Stanley. "With film music, you will have vinyl collectors competing with film buffs and fans of actors featured in the film, for example."

There are also obsessive classical music fans who regard CDs and digital recording with disgust. They will have rooms full of vinyl recordings of classical greats, including several different recordings of the same works presided over by different conductors.

Collectors used to buy records at fairs (there are about 50 vinyl fairs each month around Britain) or through Record Collector magazine. But the arrival of the internet, and eBay in particular, has made buying and selling much easier.

When it comes to finding gems, try rummaging in charity shops and car boot sales, although it is harder to pick up real "finds" as the public is becoming more savvy.

Many collectors befriend specialist dealers and hang around record fairs, auctions and websites to hunt down what they're after.

Play It Again

Prices

Anything from nothing at all to well over £17,000 for a special pressing of a Beatles record in mint condition.

More information

www.vip-24.com, the site for all the record fairs in Britain; www.legends.gemm.com, general vinyl site; www.allmusic.com, an excellent record source and database; www.birdpages.co.uk, a big directory of record dealers; www.recordfinders.com, vinyl hunting and auctions.

2004 events

11 September: Olympia Music Fair, Olympia, London. The country's largest selection of vinyl and memorabilia, sold by traders from around the world.