Hi Dan,

Depends on who or how was program the OTS, Keep in mind that the user can change the voicing on the OTS, and if you are talking about Factory styles (with the Factory OTS), many styles are carry over some keyboard model generations, therefore,
different style designers/programers that have some different criteria and taste.
And perhaps a second designer when implemented a previous style into a new keyboard and just re-voice it using the new Tone generation/Technologies, maybe just using the primary voice R1.

Here an idea of what can be done by the User as an example, OTS1 will be a single voice, OTS2 an alternative solo voice, OTS3 could be a layer, and for the OTS4 a layer that would include Voice-Harmony, and very much like the style variations, the first one is the most basic to a more complex variation.