Gary, I km not that familiar with the Yamaha Way, but on Roland’s there was a dedicated NTA channel that output the chord information only (derived from what you are playing). It’s basically the output of the chord recognition once it figures out the chord (rather than what you actually played, for instance if you are using chord shortcuts or one finger stuff).

Is it possible to send that to the harmonizer? That’s what’s basically happening with internal harmonizers, I believe.