If a DJ were to do that, they might as well stick with a CD player and a pre-set playlist. There's just a teensy bit more to it than that (as I'm sure you know fine well ).
Why not? There's aspects which aren't easy to teach, sure (judging the mood of a room, and choosing tracks to suit, for example) - but there's a lot that can be taught, for all that most of us probably learned it the hard way.
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