Vortex Sound Research

If I were to think of synth timbres that would sound appropriate in what would otherwise be purely acoustic folk, I'd think of marimba plucks, square wave flutes, unobtrusive saw wave pads (no phasing whooshes), and maybe an e. piano or some other glass-like sound if it's FM. I'm definitely missing a few timbres in that description, and what I'm looking for might not even do all the prior tones. The point is, what's a good synth for unobtrusively complimenting folk? Bonus if it's not FM.