When the envelope arrives from this music festival, you clear everything off the dining room table. You unplug the phone, get a half dozen pencils (with erasers), a large notepad and spread out the 2 X 2 1/2 ft (60X75 cm) schedule of events and begin to formulate tactics for dealing with this event. It is not easy.

Since its beginning eight years ago, "La Folle Journée á Nantes" (The Crazy Day at Nantes) has been a combination of a regular music festival and the idea of Woodstock. The festival's director, René Martin, had the daffy and diabolical idea to take a month-long music festival and cram it into a single weekend. So there are actually three crazy days during which you have to choose between 200 different concerts spread out in seven different halls. Be sure to pack a canteen of water in your backpack and plenty of things to nibble on. The scheduling might not include a food break.

The festival, from January 25 through 27, this year featuring the twin giants Mozart and Haydn, occupied the entire huge Congress Centre in Nantes. Like Woodstock, concerts are performed from morning to night and, like Woodstock, it is possible to overdose - but in this case it could be an overdose of these two classical masters. The huge convention centre is divided into different sized venues and given appropriate names: Auditorium Esterházy (2000 seats), Salle Salieri (800 seats), Salle Da Ponte (300 seats), etc. At any one time, there could be Haydn symphonies in one hall, a violinist playing sonatas in another, a piano quintet in a third, a flute and harp concerto in a forth. A series of lectures by noted scholars on Mozart and Haydn are being held, of course, concurrent with all the other events.

Each time you select an artist or composition you want to hear, you will miss six or seven other performers or groups in the other locations. By the time you have made a final decision about each concert you want to attend, taking care that you are not hearing the same work twice in the weekend, your scheduling chart might look more like a Jackson Pollock painting than anything else.

The performers were mostly young-but-already-important performers with a few greying veterans in the mix (like master pianist Nelson Friere and conductor Charles Dutoit.) An emphasis on historically informed performance practice is evidenced by groups like Concerto Köln and La Petite Band who share stages with the more traditional Orchestre National de France and the Netherlands Chamber Orchestra.

For example, if you like the intelligent young pianist Frank Braley - one of the rare pianist who knows the difference between passion and bombast - you would find ample opportunity to hear him here. He has performances on all three days, including Sunday's Mozart Sonata for Four Hands, K. 497 with Anne Queffélec (6:30pm, Salle Solomon) and a late Saturday night concert with Haydn sonatas and the Mozart Sonata in F, K. 332 (11:15pm, Salle Da Ponte). But if you heard the buzz about the young cellist Gauthier Capuçon you only have one chance to catch him in concert with the Orchestre National Bordeaux Aquitaine, Hans Graf conducting, at 11am on Saturday playing the Haydn Concerto in C.

If you like big works with chorus, Friday evening featured the Mozart "Requiem" K. 626, with the Ensemble Vocal et Instrumental de Lausanne, conductor Michel Corboz. This was followed immediately - and appropriately, I guess - by Haydn's "The Creation" with Marcus Creed conducting the Akademie für Alte Musik Berlin and the RIAS-Kammerchor. Still want more? Saturday had the "Seven Last Words of Christ" of Haydn (version for soloists, chorus and orchestra) with the Sinfonia Varsovia and the Chamber Choir Accentus at 4:15pm in the Auditorium Esterházy (Accentus just a few days before received an award on national television as "Best Vocal Ensemble.") Later, at 8:15 in the same auditorium Charles Dutoit conducted the Orchestre National de France in a blazing performance of Haydn's "Mass in Time of War." Can't stop now? This was followed by another K. 626 Requiem (the second that day!) Near midnight you could hear Mozart's "Vesperae solennes de confessore" (K. 339) and a "Missa Brevis" (K. 259) all performed by Peter Neumann conducting the Collegium Cartusianum and the Kölner Kammerchor.

If you forget your alarm clock you might not wake up in time to make Marcia Hadjimarkos playing works by Mozart and Haydn on a restored 1789 pianoforte at 9:30am Sunday. If your inclination is toward the quartets, the big ones are all in Nantes for the festival: the Prazák, the Ysaÿe, the Festetics and the Lindsay, along with the hot young Trio Wanderer.

The audiences here dress informally. Going up and down the stairs, you find families lunching on the steps, young people listening to music on headsets, musicians in tuxedos talking to audience members, couples consulting their maps for the next concert location and lots of children. This festival is affirmatively democratic and, with an average ticket price of about 10 euros, parents can bring their (mostly well-behaved) children and many do.

It might be good counsel to unwind a bit and add on a day or so and see the old part of Nantes and sample some of their famed seafood restaurants. This gathering, certainly one of the most intense, provoking and popular (almost 100,000 tickets sold this year) of those ever-increasing festival venues around France, could very well influence the structure of festivals as we know them. Young audiences grew up with sensory overload and this one certainly provides that in abundance. The success of this critical mass of young talent and the media attention it engenders makes this one of the most discussed of the French musical happenings. The festival website, www.lafollejournee-nantes.com has all the information and next year, we understand, will feature Italian masters. You have been warned.

Frank Cadenhead

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