AIX-EN-PROVENCE, France — Officially, the small square in front of the former residence of the archbishop, in the historic center of this elegant Provençal town, is named after the martyrs of the French Resistance. But every summer, the musicians, administrators and theater professionals who flock here for the Aix-en-Provence Festival give it a nickname drawn from the opening scene of Bizet’s “Carmen”: “La Place Chacun Passe” — the square where everybody comes and goes.

Over the course of four days, I watched its cafe tables fill with multilingual crowds of young musicians studying at the festival’s summer academy, librettists, composers, directors, critics and representatives of opera houses from around the world. So many singers stopped by to nurse their voices between master classes and performances that by the end of the week, the cafe had run out of camomile tea.

The one person missing from the square was Bernard Foccroulle, the Belgian organist, composer and impresario who has run the festival since 2007 and who has done much to spread Aix’s reputation as an incubator of innovative music theater — and a brand that, thanks to an ever-growing network of co-producers, is leaving its mark on opera houses and concert halls around the world.