This summary is not the rule. The rule text controls.
A judge in a Tennessee court usually cannot bring in witnesses on their own. This job is left to the people involved in the case, the plaintiff and the defendant (or the prosecution and defense in a criminal case). The only exceptions are unusual situations or when the judge appoints an expert witness under a different rule. If a judge does call a witness, every side in the case still gets the chance to cross-examine that witness like any other.
Even though judges cannot usually call witnesses, they are allowed to ask questions of witnesses who are already testifying. This lets the judge clear up confusion or get more information, but it does not give the judge free rein to take over questioning like a lawyer would.
If a lawyer disagrees with the judge calling a witness or thinks the judge is asking questions the wrong way, they can object. That objection can happen right away, or if the jury is in the room, the lawyer can wait until the jury steps out to raise the issue. This keeps the jury from hearing arguments about the judge's own conduct during the trial.
