Hit 200 notes in a row. This can be done on any difficulty and you don't need to "perfect" the note, just don't break streak. You can also use the drum kit buttons instead of the pads.
If you don't have a kit but happen to have the RB3 MIDI PRO-Adapter, set it to D for drums and use the buttons. (Note that you won't be able to hit any white kick pedal notes this way.)
An easy song for this cheevo is Lay Down Sally by Eric Clapton. Choose the Recruit difficulty and it's almost entirely red notes and no kick.