What do you do when you're the soloist in a concerto, and the orchestra director starts the piece without you? This happened to me during a high school orchestra concert. I played the bass, and the director accompanied me on piano. It dawned on me, as the applause after the previous piece ended, that we'd never discussed how we'd begin the concerto. So, after a barely perceptible nod, the director began playing the piece without me. I thought, "Do I just start playing at a moment that sounds semi-natural? What should I do?" A few bars in, I said to the director, "No, no...Stop...Please." Then, I said to the audience, "Take two...We're going to get this right!"
Fortunately, the director and the audience laughed. The director then gave me a more obvious cue to begin, and the second take went off without a hitch. Here's hoping that anyone in a similar scenario gets the chance to start the piece over before an understanding audience and director.