Ed,
I do have the harmonizer installed. It is strictly a Vocoder. It "sings" the notes you play on the keyboard. It doesn't have automatic chordal harmony.
You can assign it to left split, right split or midi. It has options to have the voices sound an octave above or below your voice, plus "True". The default setting seems to work best for me. It keeps the notes close to the octave in which I'm singing and sounds very natural.
The mic and harmonizer each have 3-band e.q. and effects settings.
I have started to like the harmonizer a little better, but you must put a little thought into using it. If you are singing a C note (in the key of C) and you push an E and G, for example on the keyboard you will have three part harmony. If you just press one key, you will have one harmony voice. If you press 3 keys you will have 3 harmony notes sounding.
It does allow you to do some interesting things such as hold a note with your voice and do moving harmonies.
On/off can be assigned to the Ketron footswitch (optional). If you install the harmonizer it will be essential to have the footswitch because there isn't a really simple way to turn it off or on with your hand. You must change screens to do that.
Big drawback: there is no indicator light or signal when the harmonizer is active or off.
I have asked Ketron to address this in a software update, but so far AJ has not responded to it.
Every time I call up a registration, the harmonizer defalts to "on", so before starting I must remember to push the foot switch to which I have assigned the harmonizer, since I rarely want to start a song with the vocal harmony on.
The jury is still out on whether I will continue to use the harmonizer or go to an external one. I'm trying to keep the setup really simple and prefer to use the internal one for that reason.
DonM