By Antony Bruno DENVER (Billboard) - The October 28 launch of “Guitar Hero III: Legends of Rock” struck the first chord in a highly anticipated battle of the bands between music-based videogames that will only get louder when rival “Rock Band” arrives November 20. Both games have captured the imagination of a music industry desperate for not only new sources of revenue but also for products that make music fans excited again.

The games’ on-disc soundtracks license 125 tracks between them, and music itself is treated as the star of each game — fans virtually play along using a variety of instrument-based controllers and in-game prompts. Both titles allow fans to buy and download additional tracks not included in the original game via an online store accessible directly from the game console, with record labels getting a cut of each.

Prices and availability have not yet been announced for either game, but the downloadable songs for “Guitar Hero II” cost $5 for a pack of three — and moved more than 650,000 units (totaling more than 2 million songs), according to Activision. “Guitar Hero” is the incumbent here, in a sense.

The first two installments of the franchise sold a total of 6 million units, a bona fide blockbuster for any game genre but particularly eyebrow-raising, considering that the game’s publisher (RedOctane) and developer (Harmonix) were relatively niche players in the videogame industry.