Hi Mark. On p128 of the Users Guide: "Full Range Chord. With this chord fingering mode, you can use the full range of the keyboard to play chords and the melody."
In the Reference section, p306, it goes on to say "With Full Range Chord, when the lowest note fingered is a certain distance from the neighboring note, the chord is interpreted as a fraction chord." That makes sense, and it's similar to the approach Yamaha used to use on their lower-end style pianos like the DGX-525, etc.
I geek this stuff, and I'm convinced that the CT-S500 is the best low-priced arranger right now.
I'm not a skilled musician, I like the option of being able to play a major chord by pressing a single note. That makes a lot of things easier, while still retaining the ability to play slash chords and other advanced chords if desired. The limitations of the CT-S models are no style editing capability, and a really weak MIDI implementation.
The CT-X3000 and CT-X5000 have style editing. But these use a tiny, cluttered LCD display, an obtuse menu structure, and a dreadful keybed. The CT-S series addresses these just criticisms. I personally have no use for the vocalizer in the CT-S1000V. IMO they should offer an upscale CT-S with 5-pin MIDI, "chord judge," and style editing. My $.02.