Hey there, Billy Joel. It's been "The Longest Time" since I've seen you, man. You've put on weight. Your hair — what's left of it, anyway — is white. And, got to admit, it was a little troubling when you couldn't remember the name of the club where you first played here, and where the likes of me (then a cub reporter and weekend WMMR DJ) first caught the Billy Joel bug.

To jog your mind, William, it was Bryn Mawr's Main Point, Feb. 10, 1972, opening for Tim Hardin, where one of the songs you introduced was a firecracker called "Captain Jack" that soon after ignited your career locally, then nationally (and that you still perform in Philly, though nowhere else).

A much bigger bummer,  as you half-apologetically, half-jokingly reminded the crowd at Saturday night's show at Citizens Bank Park, is that you haven't been burning the midnight oil, cranking out new material. Not like the doggedly determined  and ambitious "Entertainer" you used to be. The last time you swam in a creative "River of Dreams" and summoned up a new pop set was 1993. A mere quarter of a century ago.

Yet despite that, you still managed to stuff CBP for a record-breaking fourth-consecutive-summer sold-out concert (one that was honored by Mayor Kenney, who declared Sept. 9 Billy Joel Day in Philadelphia). And it was with a crowd as heavily stocked with millennials and Gen Xers (some of whom weren't even born, you noted, when some of your songs first hit) as it was with Boomers.

Better still, Bill, you and your super-pumped eight-piece backing band roused us onto our feet and were fully engaged through this slam-bang, 2½-hour song-athon. It was a show blessed with deep cuts as well as full-bore hits, including a nod ("Everybody Loves You Now") to that very first solo album  (1971's Cold Spring Harbor) that even you "don't own," you joked.

The night also offered several audience-participation picks (What's it going to be, folks? The overplayed "Just the Way You Are" or the best-of-times "Summer, Highland Falls"?) and interesting covers (nods to the late Glenn Frey with "Take It Easy" and to the 50th anniversary of Sgt. Pepper's Lonely Hearts Club Band with "A Day in the Life").

Adding to the party spirit were so many impromptu sing-alongs that the event could almost have been billed as "the Audience With Billy Joel." The collective fan-club chorus loudly joined in on everything from the show-opening (and vividly video-illustrated) "We Didn't Start the Fire" to the "Day in the Life"-ish "Scenes From an Italian Restaurant,"  "Still Rock and Roll to Me," "It's Just a Fantasy," and the signature "Piano Man," a moldy oldie still on the must-play list at bar mitzvahs and Sweet Sixteens.

So how do we explain your longevity in this "What have you done for me lately?" eight-seconds-of-fame kind of world?

It certainly helps that your chops are still in good shape. Your fingers still fly across the keyboard — fun to watch via overhead-cam video shots — as you tickle, tease, and pound out those royally rockin', jammin' jazz, barrelhouse blues, and classically inspired chromatics.

To these ears, your voice — singing and speaking — sounded overly reedy (with a tad too much electronic sweetening) on the first few numbers. Then, nearing the end of the vocally taxing night, it was pretty clear your backup singer, Mike DelGuidice, was doing all the heavy high-note lifting on "Uptown Girl."

But for the most part, we heard the same stout Billy Joel we've long admired — putting those wry, aching, and rueful tones into the put-downs of the socially inept "Big Shot" and the American dream gone sour in "Allentown," celebrating the breaking-free spirit of "Movin' Out," the sassy, neo-doo-wop of "Say Goodbye to Hollywood," and romantic pining of "She's Always a Woman."

And let's face it — it's not just you who's "not writing songs like they used to." Hardly anyone else is, either. Or at least, not writing them with the emotional and musical clout to land and score attention on today's mainstream media outlets. (Sting, Paul Simon, Duncan Sheik, and Paul McCartney ain't hitting the charts, either.) To many kids brought up on rhythm-centric hip hop, minimalist teeny pop, and mind-numbing electronica, "old school" story songs with sophisticated structure and rhyming — rooted in classical etudes and waltz time, Broadway bombast, street corner harmony, and Tin Pan Alley polish — are written off as corny, sappy, self-indulgent.

And isn't that a pity when so many others of us are "still in a mood for a melody" and talented piano men could still get us "feelin' alright"?