Mike not sure if you have solved your problem yet but here is what I would try...
Activate the LEFT voice on the Tyros, something with sustain like Organ or Strings. Now when you play single-finger chords the Tyros will output 3- and 4- note triads on MIDI channel 2 which should be recognized by the vocalizer.

If you don't want to *hear* the LH voice, just turn down the volume on that track.

For most styles the Pad and some other channels should contain useful chord data:
11- Bass
12- Chord 1
13- Chord 2
14- Pad
The pad pretty much just plays a sustained chord.

Give it a try, let us know if this works. Note I have a PSR-3000 so the channels might be different, but I doubt it.

Ted Sowirka