Actually, most hardware harmony machines (if they have a MIDI in) and most software auto-tune type programs can do this. In fact, it is common in studios to give the pitch correction a MIDI guideline to follow (if you aren't hand-drawing the pitch correction), because the half steps of the scale always give the pitch correction fits if set to correct to the nearest half step.
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An arranger is just a tool. What matters is what you build with it..!