sentences:  Activision later revealed that both "Guitar Hero 5" and "Band Hero" would support playing songs from both "Guitar Hero World Tour" (both on-disc and downloadable content) and "Guitar Hero Smash Hits", with music licensing being the only limiting factor on which songs could be made forward-compatible.The large number of "Guitar Hero" and "Rock Band" titles on the market is considered to be partially responsible for the sharp decline of music game sales in the latter half of 2009, along with the effects of the late-2000s recession.The market for rhythm games was $1.4 billion in 2008, but dropped to $700 million (a 50% decrease) in 2009 even though more titles were available that year.