There was a very rigorous technical rehearsal period up to that point.

I'll be as bold as to suggest you saw the info on the technical rehearsal, mistook it for the real thing and typed that jolly tweet yourself.

They are about to enter a gruelling phase of 12-hour days in technical rehearsals.

The performers will turn up only on the day they are needed; the directors will use stand-ins for the technical rehearsals.

On a larger scale, technical rehearsals may be held in the days or weeks leading up to a concert.