i'm afraid digitech does not have any vocal harmonizer among their products. i just checked their website. they have modeling and processing units, but no harmonizer.
i also own and use a digitech rp50, the smalest of their modeling unit for my guitar. was very cheap, and of course not very good. quite noisy, but does a honest job, i am satisfied with it.
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Yamaha S770, Studio One 3, EMU 0404USB, ESI, ATH, Dell. And others.