I have the GPO, 2nd edition & Garritan Gofriller Solo Cello and had written pieces with these sounds powered by Native Instruments Kontakt Player v.2. Thats how these libraries were originally sold. If I purchase a new version of ARIA will older compositions written with GPO & Kontakt still play back using ARIA?
Aria is the sample player which replaces Kontakt. All of the current versions of the Garritan Libraries have been re-programmed so they function in Aria, and improvements and new instruments were also added to these new versions.
But the Gofriller Cello was discontinued several years ago, so it hasn't been ported into Aria.
Only Libraries specifically adapted to Aria will play in it.
That means your old GPO won't play in Aria either. BUT the good news is that you can use Aria right alongside instances of KP2 in the same project. So even if you upgraded to the current GPO4 with Aria, you would be able to use your Cello playing in an instance of KP2.