Works as advertised Rated 5 out of 5 stars

but shouldn't the grey-white bar at the bottom (x-axis) be colored?

At least it woud be a good idea to add an x-axis and y-axis including the basic unit and that are scaled for reference. Otherwise you can't even estimate the frequencies that match a peak value.

This review is for a previous version of the add-on (1.0.0).