When a secret society comes with its own strange customs, highly developed jargon, and a belief that certain talented youth are destined for greatness, you can only be talking about the world of Harry Potter.

Or classical music.

Thursday night at the Mann Center, it turns out, these two insider cultures had quite a bit to say to each other. Harry Potter and the Sorcerer's Stone was given a world premiere of sorts. The John Williams score was stripped from the sound track and instead played live by the Philadelphia Orchestra while the 2001 film was shown on large screens. This new live-orchestra version now travels to orchestras around the world.

The night was a coup for the Mann. Some orchestral concerts struggle to make the 13,500-seat venue look respectably populated. This one, however, set a record as the best-attended orchestral event in at least recent years, and maybe ever, Mann leaders believe. Ticket sales were stopped at 10,700 because of concerns that any more would mean a less comfortable experience for all those near-Muggles. A lovely problem to have, this.

And the rain? It was uncomfortable only perhaps for those who refused to see the plastic ponchos Mann staff handed out as the invisibility cloaks they clearly were.

It's a phenomenon well worth considering that you can show up to a movie theater these days and find yourself as one of just a dozen viewers, and that classical leaders are focused on dwindling attendance, and yet when you put the two experiences together in an event like this, a vast crowd blooms.

This was a dream audience - knowing and demonstrative, tracking the film with split-second cheers, and generally quite young. The "Yes, but" argument that usually greets these film-orchestra marriages didn't apply here: If the audience was sometimes unaware that 90 percent of the adrenaline was coming by way of the music, they saved their loudest praise for the end, after the action was over and the orchestra and conductor Justin Freer stood. Listeners understood that they may never again hear a closing-credit sequence played by a major orchestra with such polish, power, and conviction, and most listeners stayed to the last note.

A word about John Williams. The Philadelphia Orchestra has recently taken up his cause, programming both his film and "pure concert" music. I can't think of any reasons for wanting to hear his Cello Concerto again. Film music, on the other hand, is also an art form, and Harry Potter is among Williams' most inspired soundscapes. The orchestra was superbly rehearsed, and the sound amplified but well blended (the chorus track was recorded).

Williams does not use a formal Wagnerian leitmotif system for particular characters or ideas, but there is a whiff of it: a legato love theme; the sound of flying that draws its sense of lift from quickly gliding violin runs; and even the rhythm of the words Harry Pot-ter crosshatched onto a four-note melody that clearly telegraphs triumph.

That this film so heavily leans on music makes it a good choice for an orchestra, and that it demands virtuosity and heart made it an uncommonly satisfying fit for this one. The way the deep sound of pizzicato notes can propel momentum, the extent to which an incisive brass section can menace, the full-ensemble soar - all these things extend meaning.

But only when they are played by a great orchestra do they reach full storytelling potential. The ensemble in the original sound track was fine, as no doubt will be many in the cities where this live-orchestra version goes next. But for sheer impact, it's safe to say few audiences elsewhere will discover what we did at the Mann: that a decade and a half after its premiere, this movie had finally reached its most perfectly realized form.