Yamaha CS80

Greetings.  This is my second post to the group.  I've been lurking a
while, and enjoyed reading every post from the beginning.  I'm
impressed by the knowledge and experience represented here.  I don't
have a CS-80 and only touched one once in a music store in Plymouth,
Michigan.  I've been in awe of the CS-80 ever since hearing the first
UK album.  Who would't be?  I never studied how the synth was laid out
or why it was so expressive.  It was more of an icon in my mind. 
Ironically, it was the CS-80V softsynth that piqued my curiousity to
learn more about the original.  I'm not an electronics guy like old
crow, David R., and others here, but I am fascinated by the design
decisions of the orginal engineers.

I've been curious about a particular CS-80 sound that I'd like to ask
about.  I posted a short mp3 in the files section: 
CS80_Chorus_Studio.mp3.  It's the last part of the "Alaska" intro.  At
0:16 you can hear chorus being switched on.  I believe Eddie Jobson
ran his CS-80 through a Roland RE-301 or RE-501 Chorus Echo.  My
question:  Is this the CS-80 chorus or the Roland chorus being
engaged?

My theroy:  The entire "Alaska" intro is run thru the Roland Chorus
Echo with its chorus on.  And the sound at 0:16 is the CS-80 chorus
being engaged.

Another curiousity is the subtle major third interval that comes
through at 0:14.  It sounds like filter resonance, doesn't it?  But
how is he doing it?  I would guess he's tweaking the filter resonance
lever (next to the initial pitchbend lever), but both hands are on the
keyboard at this point.  I've always been curious about this.

Anyway, thanks for hearing me out and for your insight.

-bart