musicmad are you sure about that? I’m not an expert on digital processing but there is clearly a conversion process happening (which will itself cause some fractional amount of latency) but surely even transposing a full chord still needs to know the starting point for applying the transpose processing?
There is an algorithm on WIKI. I learned it briefly and I think it does not need to know the "main" note. It shifts the whole spectrum or main part of it which is important for a guitar.