The last weekly update of songs will come on April 2, with "what we feel is an appropriate track for the final release," said Harmonix.
"We have managed to maintain a consistent release schedule for a staggering 275 consecutive weeks, releasing over 4,000 songs for the Rock Band Platform, but in recent months we've scaled production down as we've transitioned resources onto other projects," Harmonix said.
The studio added that it has "several new titles in development" and needs developers on those projects to "usher these new games along." Those requirements prevent the company from maintaining a less frequent, semi-regular schedule, Harmonix explained.
According to Harmonix, the weeks between now and April 2 will see the rest of the Rock Band Blitz songs be added to the Rock Band catalog, as well as Pro Guitar upgrades for existing songs and new tracks by artists that have not previously appeared in a Rock Band game. The company is also continuing its sale of 50 percent discounts on more than 1,100 Rock Band songs.
"We're incredibly proud of the DLC milestones we've set, especially producing the largest music library of any game available, and we wouldn't have been able to release as much outstanding content without the support of our amazing community," Harmonix said.
"an appropriate track for the final release" will arrive when the schedule ends April 2
Harmonix also posted an FAQ about the announcement in the Rock Band forums.
"We don't have any Rock Band titles in active development at the moment," the studio said, "but you can expect us to continue to support the existing titles and the extensive song library." Harmonix isn't actively licensing any more music for DLC songs, but didn't rule out the chance for future additions to the Rock Band catalog "should the right band and the right opportunity arise."
Harmonix assured Rock Band fans that the franchise's network components — the Rock Central servers, Music Store and online leaderboards — "should continue to run without interruption for the foreseeable future." That includes the user-generated Rock Band Network on Xbox 360, although because Harmonix itself releases Rock Band Network songs on PlayStation 3, players on that console won't get new Rock Band Network tracks after the weekly DLC schedule ends April 2.
"We're not breaking up the band, but we are taking a break from 5+ years of weekly performances," Harmonix said.