I think the big mistake everybody makes with VH machines is over-use of the 3 note harmony. You listen to most pop music, and most of the time, it is only ONE part on top of the melody (or underneath it, or jumping from above to below!), or at most, one voice above, one voice below.
Going for the big Carpenter's sound is something done rarely. Or at least, far less than the simple stuff.
TBH, most arrangers don't offer the kinds of control I would want to use if VH was a part of my act (it isn't!). I would like easy footswitch control of whether the harmony part was above or below me (on the fly) and an easy way to go from one part to two and back (and off) without taking my hands off the keyboard.
But big block harmonies that drone on and on is such a dead giveaway of a nasty VH! Less is more...
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An arranger is just a tool. What matters is what you build with it..!