I don't perceive any chypre base in the Labo Ylang. It's a big floral up top, the drydown is somewhat clean and not chypre (the chypre base, if present, comes in the drydown). Indeed, there is simply no old chypre around, because the key ingredient, oakmoss, is now severely restricted. There are some fragrances that try to replicate some of the aspects of a chypre base via different combinations (eg patchouli-vetiver type of combos), but they don't smell quite like old chypres (though they may smell good on their own).
If you are old enough (>40 yrs old), you'll certainly recognize the smell of a chypre base as something that was in the air back then, even though you won't be able to connect it to any specific perfume.
Mitsouko has been reformulated a few times. The debate is still on about whether the current version is ok - there was some talk that the Guerlain perfumer was able to distill oakmoss without the IFRA offending component, but I don't know how it ended up.
Edited by cacio - 6/20/13 at 8:17am