Yes, I'm surprised too. Rock Band Blitz, despite its superficial similarity to Harmonix's PS2 music games Frequency and Amplitude, is fundamentally different from those -- and from Rock Band. Well, okay, you're still hitting buttons in time to music, represented by icons coming down the screen. It's notthat far gone.
But almost everything else has been rethought. Instead of Rock Band's five "buttons" per instrument or Frequency's three, each instrument track in Blitz is limited to two tracks, with imported tracks converted algorithmically from the original Rock Band version. It is, technically, a simplification, but it's still challenging enough when you're juggling four or five instruments. And when you're playing "Symphony of Destruction."