Double neck. But different...

[Basvarken]

Here's a remarkable double neck acoustic guitar by the French brand Lag, that I spotted on the Messe.

[Dave W]

It looks more practical than the usual doubleneck. Any idea how the two necks differ, or is it just for different tunings?

[Basvarken]

I think it's a brilliant concept. Can't believe it hasn't been done before (that I know of).
I have no idea how the second neck differs. I only saw it in this situation being played live (only on this side)