I use the Harmony-M. I sounds great, a bit more realistic than my Digitech VR, and far better than the PSR-3000's onboard harmonizer.
Dave, TC Helicon makes a Harmony-G for guitar players. You may want to look into that unit. Less money, very realistic, very compact too.
Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)