They’re just recordings of phrases. VOP has a few patches where you can play your own lines, but…they are not very good.
Forgotten Voices Francesca/Barbary/Terrie/Cait are all pretty great, but it’s an old Tonehammer library, and as a result - the library is not well-organised. For example, you have to do a lot of auditioning to even find a phrase that fits the key of your work. Sure you can use the pitch-bending features as well, but the Forgotten Voices libraries are not easy to use. You generally have to compose around the vocals - which is not the way it should be.
Don’t get me wrong, they are GREAT recordings, but the Kontakt scripting is very…2009!
On the other hand, if you want something easy to use - you should also look at Sonokinetic Aliye and Sonokinetic Rojin.
Aliye - http://www.sonokinetic.net/products/ethnic/aliye/
Rojin - http://www.sonokinetic.net/products/ethnic/rojin/
These libraries are similar to Forgotten Voices - but they make it MUCH easier to integrate into your music, as in the Kontakt interface you can change the key of some of the phrases - and they recorded different phrases for different keys. Plus, they are tempo-synced.
I particularly like Aliye - they really captured a powerful vocal - and if you put her voice through a nice reverb, it really sounds phenomenal.