When is selling 595,000 copies of a game in three weeks a disappointment? When it’s the Beatles edition of Rock Band.

The sales make it the third best-selling game of September, beating out fellow debutante Guitar Hero 5, which just fell short of the 500,000. The Beatles game was up in second place for total revenue thanks to sales of the higher-priced editions with customized guitars, though there aren’t any public details of how well each individual version sold. Given that the only real extra cost per unit with the custom controllers (compared with the standard guitars) is any licensing fee, you’d have to imagine the profit margin on the accessories is very healthy.

There had been predictions of a million sales for the game in the month, a figure Guitar Hero III achieved. Now some analysts are questioning the Beatles game’s staying power, though it’s not exactly as if the tracks are going to fall out of fashion, and it should certainly get a boost from the Christmas market.

Meanwhile the rhythm game genre keeps on rocking. There’s now a version of Rock Band as an iPhone app, costing $9.99. The game includes 20 songs, with others available at 99 cents for two songs.

While the DS version of Guitar Hero solved the touchscreen conundrum by releasing a plug-in keypad, this game requires users to tap along on the screen, Tap Tap Revenge-style. Early reviews are fairly mixed, though it’s possible that the price tag will mean it’s mainly people who are dedicated to the Rock Band series who’ll buy it, so they’ll be less likely to be disappointed.

For those looking for a more intense musical game experience, Brutal Legend could be for you. Released this month, it appears to be the perfect answer to that age-old question “Why isn’t there a game like Grand Theft Auto where you play a roadie, everything is themed on heavy metal album covers, the main weapon is a Flying V guitar which can fire pyrotechnics, and missions include summoning an army of fans by playing a Guitar Hero-style rhythm game?”