I've had a quick listen but I can't save the file for some reason, only play it in WMP. I'm working as well so it's on real quiet.
The strings aren't playing chords, just sounds like Bb, C and G in the first 4 bars, like this: 2 bars on Bb, 1 bar on C and 1 bar on G.
You could play this if that's a lil thin: 2 bars with G & Bb, 1 bar with A & C and 1 bar with D & G. Left notes being the root.
The Guitar pluck is Bb - A - G with a little bend on the A-G.
There's a fair few chords that would work over it as well if you wanted to add something. Gm for 2 bars, FMaj for 1 bar, FMaj 1st inversion ( A, C, F ) for 1/2 a bar, Adim for 1/2 bar returning to
Gminor again or something.
You could play 7ths too, there's a strong sense of a Cmin7 and a Dmin7 in there but if you play just Gmin and FMaj in this way: Gmin ( no 5th G,Bb ) FMaj ( 3rd and 5th A,C ) then Gmin ( root n 5th inverted no 3rd, just D, G ) I think that's about right, which is the same as the doubled up notes I said earlier.