What is the use of the Filler Field?

I developed FCPX AutoDuck essentially to solve my personal problem (the ducking) for a podcast that I produce (!) With Final Cut Pro X.

[Alex Raccuglia, main developer]

The Filler serves me to add music (background) when there is none in the music track.

But maybe it’s faster to show you how it works:

The Filler puts some “filler” music (you specify) when the Music track is silent.