On a canopied stage and via a pair of jumbotrons, the musical unfolded in this concert version, a modification of director Christopher Ashley’s more complex turntable staging. The voices and the orchestra mixed exhilaratingly on the Mall, and the music, redolent of the Celtic influences on the maritime province, seemed to have a supercharged, spirit-lifting impact on this occasion. Sankoff and Hein’s score culminates for me near the evening’s end during “Somewhere in the Middle of Nowhere,” an unabashedly sentimental bon voyage song that I never tire of hearing: “Something in the middle of nowhere,” it goes, “in the middle of clear blue air, you found your heart, but left a part of you behind.”