Glad I'm not the only middle-ager here.
I believe I saw a production of Mozart's "Magic Flute" at the old Juilliard building on 122nd St. sometime in '62 or 63 but I could be wrong about the year. Sometime in '62 I was also taken to see "How to Succeed..." but, at age 7, I don't have very strong memories of it (though I vividly recall the movie version in '67)
The first on-Bway musical I actually have memories of is "Ben Franklin in Paris" with Robert Preston (same, year, I recall as High Spirits, '64). However, earlier that year I saw a review featuring Tom Glazer's "On Top of Spaghetti" by the Paper Bag Players. (Tom, btw, sadly died this year.)
But the event that really did it for me was seeing Man of La Mancha at the ANTA Washington Square Theatre in late '65. I think it was one of the preview performances before the opening. I recall to this day that my Mother actually injured her hand and burst a blood vessel or two from applauding as hard as she did.
Being involved in an artistic effort that could so affect human emotions became a strong desire from that moment on.
GEFTS (aka Adrian)