This is a motion sequence that applies to the performance-wide parameters which can affect all PARTs at the same time. As opposed to the motions sequence lanes which are inside each PART. The parameters available here as destinations are different.

Hi, I'm introducing to the Motion Seq

I found that there is a motion seq editing page in part 1 to 8, so there are 8 motion seq (one per part)

then I found in Edit - common / Audio another Motion Sequencer, but source mod MS Lane 1-2-3-4 are only assignable to few parameter like Ins a/b Reverb ..

this Motion sequencer that I found in Edit - common / Audio is only for use with external audio ?

Hi, welcome to Yamaha Synth!
Thanks for the question.

There are Motion Sequences available to the PARTS 1-16...
there is a separate Motion Sequencer available at the COMMON/Audio level of the architecture. It can be used to control those things that apply to the entire Performance - this includes the System Reverb and Variation Effects, the Master Effect, the Audio In which can be used as a Modulation source within MONTAGE.

So when referring to the Motion Sequencer you will see a reference to "8+1". This refers to the number of Motion Sequence Lanes that can be active. Eight LANEs applied to any of the Synth Parts, one Lane always available to the upper Common level.

A LANE is a pathway between the Motion Sequence (16-step grid) and the Synth engine.
Up to four LANEs can be used on a single Part.
Up to eight LANEs total can be used in a Performance total (directed to the Parts)
The upper level Common/Audio level Motion Sequence is always available.
Yes, you can apply it to certain parameters affecting the A/D Input.

Motion Sequence tutorial