First heard it used by a lovely Irish whistle player, Peader Finn, who described someone's playing as having 'a touch of the black dots about it' which, as you can imagine, means someone playing as if from music, not having internalised the tune, and not able to make it flow.

These days used a lot more commonly, but I would still use it with a bit of a smile- it's not a 'serious' description.