Are you talking about the bar labeled -1 or 1 in your image?

If Bar -1, it has no MIDI data so it does nothing until generated. Once generated the song has an audio track with data on it.

RB doesn't generate when you hit play.
You have to generate once to create something.

Then it won't generate again until you tell it to generate again.
One of the differences between RB and BiaB is that BiaB regenerates every time you hit play, so things change every time.
RB lets you build it right once and not worry about losing anything unless you intentionally generate or record over it. But you have to generate once.

Unless you make the first 8 tracks BB tracks, then RB behaves more like BiaB.
To try this, right-click a track, then click Track-> Make the first 8 tracks BB tracks (or close).

The first 8 tracks become blue and are now those BiaB type tracks ..

I do not work here, but the benefits are still awesome
Make your sound your own!