Activision has announced that the Guitar Hero franchise surpassed $1bn in US retail sales in just 26 months, according to figures from NPD Group.

Guitar Hero, now in its fourth iteration, has sold in excess of 14 million units in the US alone, setting an industry record.

Gamers have downloaded more than five million additional songs for Guitar Hero III: Legends of Rock in the 10 weeks since its launch, costing $2.50 each or $6.25 for three.

"Guitar Hero is one of the biggest brands and one of the most powerful distribution platforms in entertainment today," said Michael Griffith, president and chief executive at Activision Publishing.

"Guitar Hero's popularity with broad audiences is a confirmation that video games have become a true mass medium."

The original Guitar Hero was released by RedOctane in November 2005 on Sony's PlayStation 2. Activision took ownership of the franchise when it acquired RedOctane in 2006 for $100m.