Choral & Aleatoric Orchestral Libraries?

I have Spitfire's Uist which is ridiculously vast. Too expensive for what it is though.

 

From Sonokinetic check Tutti, Tutti Vox and Expressivo. From 8dio check CAGE and CASE series. From Spitfire take a look at Bernard Hermann Composer Toolkit, it has some nice classic aleatoric effects. There is also Thrill from Native Instruments (part of Kontakt 12 Ultimate), it's not fully orchestral but this might have sounds you're after. Also if you have any choral library check if there is a FX folder in the articualtion list. Most of the time they do contain some nice aleatoric choral effects.

 

I should say that I think Uist is very much worth it if on sale. The library is absolutely vast, and does things outside of horror too, like quieter passages. Recorded the same way as other Spitfire libraries and so includes mic positions and the like. There are an insane amount of well-organized articulations in there. I ultimately chose it over CAGE and the like due to a greater amount of versatility and orchestral integrity, and there's no way this library will be exhausted to the point of recognition in media. Follows the typical Albion structure and was recorded in the same place.

If you're not after purely orchestral, look into Dark Matter 2. Again, huge and well organized, and different. I tried Thrill for a bit but aside from the interesting "playability", found the sounds somewhat generic. I haven't heard anything like Dark Matter before and you can tweak the sounds in a user-friendly, versatile manner. Comes with a boatload of interesting reverbs as well. What I loved was the ability to assign each of the 8 available total sound channels into CC faders, which actually makes it quite playable. You can actually play it tonally too. It caught my attention because of Jesper Kyd's and Inon Zur's reviews.

https://www.stringaudio.com/kontakt/darkmatter2