One of the nicest things about a concert in the park is that, even if you’re late, you get to hear most of the music.

So what if there’s a snafu on the G train, as there was Wednesday night? Those of the more than 20,000 of us who flooded Prospect Park for the New York Philharmonic’s first Concert in the Parks this summer heard the rest of Tchaikovsky’s Symphony No. 4 without cooling our heels at Avery Fisher Hall until intermission.

Even from the “cheap seats” — the outer fringe of the park — the Phil’s finesse was clear. There were razor-sharp pizzicatos from the strings in the scherzo, and rich, meaty fortissimos in the final allegro. On the podium, conductor Alan Gilbert danced from side to side in his white dinner jacket, cuing a tricky syncopated passage.

After intermission, a spectacular pink and gold sunset faded over Park Slope as Gilbert returned for a pair of Respighi tone poems, “Fountains of Rome” and “Pines of Rome.”

These are easy-listening pieces, just right for leaning back and watching the stars come out. In fact, “Fountains” opened with a lazy, mysterious theme that could be the soundtrack for a New York summer night.

A tattooed young couple sipped wine and stared into each other’s eyes while, only a couple of feet away, a trio of toddlers silently ran circles around their parents, brandishing glow sticks against the gathering darkness.

Brilliant, impressionistic orchestrations showed off the Philharmonic’s easy prowess. A cascade of horn fanfares rang out clear and firm, and the shimmering strings and percussion of the last movement seemed finally to evaporate into the air.

For the more bombastic “Pines,” Gilbert whipped up quick tempos and massive fortissimo climaxes for the “Villa Borghese” theme, contrasting with the dark, mysterious harmonies of the following “Catacomb” section.

At last the bombastic “Appian Way” segment brought the concert to a crashing close: a perfect prelude to the fireworks that followed.

The program repeats tonight in Central Park, fireworks and all; on Monday night in Central Park, violin soloist James Ehnes joins for a different program.

For music this fine — and free — you might skip the train and run there.