id prob use real labs real guitar vst, they do others aswell like realstrat, reallpc, but for this 1, id use real guitar or real guitar 2, its a brilliant vst, all of them are,, watch 1 of the tutorials they have on youtube to get to grips with the strumming side of it,, easier doing that than for me to explain,,, and for the cello and ( sounds like a flute and or piccolo ), id prob use edirols orchestra, another really good vst,,
It sounds to me like it could be an organ type of sound (maybe a church organ setting on a keyboard)?!
Dougal could be right about the piccolo thing... the same notes being played an octave apart?