Spot Following

In an upcoming show we want to pick out a singer with a couple of narrow beam MLs and then follow her upstage. Now, we can't use our "P&T" on our little lighhack as both lamps will have different agendas. My original plan was to point them to spot A and record them, then point them to B and record. I would change during a 20 or 30 second cue.

But, this would require a very disciplined move every show. Is this a case where the master pair crossfaders could be used? Or would perhaps one sub with focus for A and another with focus B that we could run up? Not really sure how this would work.

So bottom line: how do we get two spots to move slowly from A to B in a controlled manner but in a variable time?. 

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