Just five years ago today, Apple introduced the first-generation 5GB iPod with the slogan: "A thousand songs in your pocket."

The diminutive device was about the size of a cigarette packet, and weighed just six ounces. And packed a punch well above its weight.

According to Apple CEO Steve Jobs at the time: "With iPod, Apple has invented a whole new category of digital music player that lets you put your entire music collection in your pocket and listen to it wherever you go. With iPod, listening to music will never be the same again.”

It took a little while before the world grew to realise quite how right he was.

The device itself was revolutionary. While MP3 players had been around for a while, they suffered in most cases from poor build quality, low capacities, slow file transfer and 'clunky' media management software.

Apple's device, in contrast, was beautiful to look at, had a 5GB capacity and integrated snugly with iTunes, itself then at version 2.

File transfer was a dawdle, as unlike competing products, the iPod used FireWire to transfer songs. This was around ten times faster than the USB 1.1 used by other players at the time, and meant you didn't have to wait overnight to transfer a thousand songs.

While critical response was muted at first, as sales climbed and critics began to comprehend what the product was about, the iPod quickly became a social trend.

Three commonly reported phenomena arose around the product: iPod jacking, podcasting and iPod DJ bars. Both trends underline the power of a private device in public disclosure of musical taste. Music is a unique area of human endeavour which is at once public and personal.

First reported in New York, iPod jacking would see strangers with iPods swap headphones to check out what each other was listening to.

And iPod bars also emerged, places at which clubbers were invited to turn up, plug in and play their favourite songs. This New York phenomenon began at Andrew Andrew and soon found international status with clubs such as the Playlist Club.

Perhaps the most mainstream cultural phenomena raised by the creation of a portable product that offered a high degree of individual control over media is podcasting.

Podcasting, best understood as radio you can listen to where, when and how you choose, has become a huge mass market phenomenon, embraced by all the world's media conglomerates. Its evolution is unlikely to have achieved such success without the iPod.

Over time, the iPod has been updated, received extra features, and transformed into the three-strong family of products - the iPod shuffle, iPod nano and iPod we know today.

The success of the product has also thrown up unexpected negative consequences, opening debate about the life-span of lithium ion battery technology, and the need for ethical manufacturing processes in an increasingly globalised age.

The iPod seems to shrug off such criticisms, and has become an international icon, its white headphones clearly creating unspoken bonds between music lovers on the move.

And that's the main point of the product. Music and music appreciation are key to its success. It exploits Apple's knowledge of user interfaces to deliver a solution that's both easy-to-use and highly effective. It's advanced technology for people who don't care about technology. A seamless solution that's focused on letting users carry their music, hear their music and share their music.

When the iPod appeared, the music industry was battered, bleeding and clueless. Sales were declining - fast - and the only solution out-of-touch industry executives could find was to pursue file-sharers and sites like Napster through the courts. They had not realised that their market had fundamentally and irreversibly changed. Steve Jobs helped them comprehend this transformation.

When, on 28 April 2003, iTunes opened for business as a music store (initially only in the US and only for Macs), that's when iPod sales hit overdrive, and when music industry execs finally understood the needs of the new market: a wide catalogue, high-quality songs; a legitimate service and a price that didn't break a music lover's heart.

In October 2003, Apple released iTunes and iPods for Windows systems. Today, most iPods sold are sold to Windows users, the company recently confirmed.

The impact on users was equally profound. "I got an iPod in early 2002," a user told Macworld. "I had always loved music, but hadn't really heard much for a while as I had fallen into a busy life. The iPod came along, and because it could carry so much music, I began to rip my CD collection to iTunes. I began to listen to music again, it was like rediscovering parts of my own personality."

At least for that music fan, the impact has been, perhaps not life-changing, but deeply positive.

"Now. Music. For me it's an addiction now. I can't walk past a music shop. And if I watch a band on the TV and like them, I'm straight into iTunes to buy their song."

Similar stories have been heard from across the planet. The impact has been that music sales have begun to slowly recover, and artists and music fans are listening to broader, deeper, wider music categories than ever before.

Former Pink Floyd manager, Peter Jenner, calls this the "evolution of a massive market of multiple niches".

Jenner predicts this tide of technological change, coupled with online music and the development of a music-savvy audience will generate more interest in different music forms, with audiences stepping away from genre-based to recommendation-based music consumption.

Apple achieved this by combining several talents: for design, for usability, for innovation and a dose of special secret sauce - the ability to fully understand the market.

Five years later, while competitors attempt to match Apple's product by features and price, they continue to fail to comprehend the market the iPod now defines.

They fail to understand the primary strength of the iPod and its surrounding ecosystem - technology for people who aren't interested in technology - a bridge between the artist and the music fan. Exactly what music and the music industry has always been about, at its best.

Apple's unique focus on giving the market what it truly needs, rather than dictating what it should need, means the company has consistently outsold, outmatched and outraged its competitors.

Since 2003, Apple has sold over a billion songs through the iTunes Store. It has sold over 60 million iPods and added £32 billion to its market capital.

Sales of digital music account for 11 per cent of overall music sales, and digital music sales are worth over $1 billion worldwide this year alone - with iTunes commanding 80 per cent of that growing market.

iPod users continue to maintain a bond with their music player, despite a series of skewed press reports asking if the product has had its day - reports that effectively try to plug the market gap left by Apple's terminally ineffective competitors.

Success has been so huge that Microsoft has revealed its Zune player, a clear attempt by that firm to capitalise on a market Apple has defined.

In this attempt, Microsoft is prepared, not for the first time, to exercise its PC OS dominance and deep, fund-filled pockets to try to dominate a market spear-headed by someone else.

But at five years old today, the iPod remains the market leading device that switches music lovers on to songs and has cast echoes across the media landscape that belie the six ounce package of its original incarnation.

To say 'Happy birthday, iPod' is also the same as welcoming its gifts: reignition of interest in music: the evolution of consumer-centric media, such as podcasting and online movie downloads; the advancement of notions of digital convergence; and the creation of a powerful market that poses significant challenge to file-sharing and music piracy.

Happy birthday, iPod.