The elegant woman seated next to me at the Sunday matinee was excited to see Sara Mearns in “Slaughter on Tenth Avenue.” This was high praise, as she had fond memories of Suzanne Farrell and Arthur Mitchell in the piece—the ballet’s original 1968 cast. The New York City Ballet’s 75th anniversary season has included several dancer celebrations, but I’d like to take a moment to toast the audience, which, on any given Sunday, is full of avid and incredibly knowledgeable Balanchine fans. I often discover that a random seatmate or a stranger behind me on the concessions line is drawing on half a century of ardent viewership. Frequently, ballet legends like Eddie Vilella and Kay Mazzo are in attendance. At that same show, I sat behind the dance historian Alastair Macaulay. I’d also brought my mother along, who would never claim to be an expert though she has watched literally hundreds of shows over the years while supporting me. There are no pennants or Patty McBride bobbleheads for these balletomanes, they come for the love of the players or the game. Maybe because I’ve logged time on both sides of the curtain now, I feel compelled to fête their allegiance to the company too. Without them, there would be no 75th anything. Like that old tree-falling-in-the-woods conundrum, does a ballet exist without spectators? It would just be fancy exercise.