Since June, the UK Top 40 has featured a hidden advertisement for chewing gum. It turns out that Chris Brown's hit Forever is a crypto-ad for Wrigley's Doublemint gum.

I recently posted an item on how the charts included a number of references to trainers - a commercial battle between Nike and Adidas conducted within the lyrics of pop songs.

But in studying the words of all the hits, I failed to spot the significance of the chorus to Brown's number. "Double your pleasure/double your fun", he sings - a line I should have twigged was from the Doublemint gum jingle used since 1960.

Now Wrigley's have come clean. In a press release they reveal how the song is an extended version of a new jingle for their product.

"The summer release of Brown's smash hit, Forever, which featured the unmistakable Doublemint gum jingle lyrics, kicked-off the creative partnership between Brown and Doublemint gum", the company announced.

"Wrigley consulted with Translation Advertising (NY) to conceptualize and identify the artists behind the jingle remakes."

Translation Advertising is co-owned by Grammy-winning rapper Jay-Z, real name Shawn Carter. With another African-American entrepreneur, Steve Stoute, they started the agency to help companies reach young multicultural consumers.

The Wrigley's campaign is aimed at the US market and includes TV ads featuring R&B singer Ne-Yo doing his own take on Big Red's "kiss a little longer" jingle and country singer Julianne Hough proclaiming that Juicy Fruit's "taste is gonna move ya".

It is the global chart success of Chris Brown's Forever that takes the campaign into new territory. No-one knew the song's secret until an article appeared in the Wall Street Journal.

Apparently, while recording the Doublemint jingle in February, Brown extended it into a four and a half minute pop song. Then, in April, Mr Brown's record label, Jive, released the song to US radio stations and digital download services as a single. It crossed the Atlantic a few weeks later and has sat in the UK charts for the last 10 weeks.

British gum-lovers will not be tempted by the rapper's jingle which is only being used in the US, and most Brown fans I suspect will be unfazed by the origins of the hit. But the story does remind us how sophisticated the advertising industry is becoming in trying to make an impact with potential customers.

The Mother advertising agency, based in London, is using theatre and film to sell product. The low-budget movie Somers Town, set around St Pancras station and due to hit the cinemas this month, is sponsored by Eurostar.

Meanwhile at the Edinburgh Festival, Pot Noodle: The Musical has played to standing ovations. Behind the scenes, most of the production's costs are being picked up by the snack manufacturer.

I don't mind being advertised to but I can't help feeling slightly abused when I discover selling is being conducted only with my subconscious. Perhaps it is a legacy of the way commercial broadcasting has clearly marked out the ads from the content in this country, but I also find it slightly disconcerting when the two become blurred.

