It seems that S670 does not work with a microphone (no effects or vocal harmonizer). Other than that, it has a lot of new voices, I'd say, rather advanced, including a new Concert Grand piano.

To my knowledge, S670 is a first Yamaha arranger at this price and weight, which has 128 voices polyphony.

Before S670 there were S650 and S550, which were rather simplified. I guess, having a competitor like Korg PA300, Yamaha had to make this MOTL arranger much closer to TOTL level.