Since some time now the Harmonic Exciter is in the beta store.
So, what is it useful for?
When ever you try a FUZZ or a Distortion/Overdrive pedal, and those wont give you the amount of distortion were you are after, the Harmonic Exciter is your friend.
Well, you could properly increase the input level, but that will as well increase the noise. The Harmonic Exciter instead create higher-order harmonics from the input which could be mixed into the original input, this will level up the input without level up the noise. The Band Pass Filter allow you to select the the frequency spectrum were you would add excitement. The “Harmonics” controller allow you to select the Level of added harmonics, and the Direct controller allow you to mix in the original signal. Of course, it has a Amp control as well, but be aware that using that will reduce the noise reduction.
This all allow you to drive your FUZZ/Distortion/Overdrive pedal on a level were it create your desired sound with a reduced noise floor.