What does "2x Bass Pedal" mean?

Many musicians use two bass pedals rather than one when they're playing their songs (especially in metal songs). To keep you from breaking something (like your leg), we thin those beats out so that they can be played on a regular, single-pedal Rock Band drum kit. But many dedicated Rock Band drummers own two bass pedals, and they are capable of playing the original chart for these songs. For this reason, many songs on the Rock Band Network are charted both for a single-pedal setup and for two bass pedals.  We mark songs that require two bass pedals for accurate play with "(2x Bass Pedal)" in the title.

Please keep in mind that this is ONLY for legacy Rock Band titles. There is no 2x Bass Pedal feature in Rock Band 4 at this time.