With a bow-tie, big glasses and quiet voice, pianist Emanuel Ax's demeanor is deceiving to any who haven't heard his rollicking, vivacious performances on stage.

		Pittsburgh Symphony Orchestra With: Andrew Davis, conductor; Emanuel Ax, pianist; Andres Cardenes, violin. Program: Vaughan Williams, "The Lark Ascending"; Shostakovich, Symphony No. 9; Beethoven, Piano Concerto No. 3; Wagner, Overture to "Tannhauser." As pianists, Davis and Ax will perform Faure's "Dolly Suite" an hour before each concert. Where: Heinz Hall, Downtown. When: 1:30 p.m. today; 8 p.m. tomorrow and Saturday. Tickets: $19-$72; 412-392-4900.

While the Pittsburgh favorite has the bearing of a person who asks for silence in a library, Ax's "shushes" -- Chopin, Schumann and Schubert -- are anything but reserved. Conservative-looking as he may be, the 56-year-old is more interested in shaking up the industry than sticking to the status quo.

Take his essay on applause, posted on his Web site, www.emanuelax.com: "All of us love applause, and so we should -- it means that the listener LIKES us! So we should welcome applause whenever it comes." But the "arcane rules" defining when to clap still have Ax shaking his head.

"I just think it is so silly to tell people how to behave at concerts ... to ask people to not applaud when they want to," he says by phone last week. "Sometimes, it takes a special energy not to applaud. If you are talking authenticity, the first thing you ought to bring back is clapping between movements. When composers write a big ending, they expect applause. Nobody at a Beethoven performance would have dreamt of not reacting at the end of the first movement of his Third Piano Concerto."

That's the work that Ax will be performing today and this weekend with the Pittsburgh Symphony Orchestra, conducted by Andrew Davis. Ax is not interested in inspiring a riot or even an interruption at Heinz Hall, but just to get the music industry to rethink some of its practices.

In fact, after the thrilling end to the first movement of the Beethoven, Ax won't be overly concerned about applause. He'll be preoccupied with the daunting task to come -- the opening phrase of the middle movement. It is here that Beethoven famously asks the performer to hold down the sustaining pedal over three measures and several different harmonies, unheard of in his day (and not that common since).

The sustain pedal -- the one on the right, also known as the loud pedal -- raises the dampers and allows all the strings to vibrate freely. "You normally change the pedal at every change of harmony, so it doesn't sound messy," says Ax. "I think [Beethoven] was looking for hazy sounds and then clarity here. He was successful doing this in the last movement of the 'Waldstein' Sonata. In the concerto, it is harder to do because the chords are closer together. I am still struggling with my foot, so the pedal comes up and it is not messy, but hazy."

The effort is worth it, as the moment is one of the more striking in the concerto repertoire.

"It is very otherworldly," says Ax. "I can't imagine what the audience would have thought in the first performances."

Ax recently has been generating situations for similar audience reaction by performing new music with more regularity, a counterpart to his period music escapades of the '90s.

"I am doing a little more about it than I did before, and I think that is healthy," he says. "I am worried about doing a program that is Haydn, Beethoven, Mozart. I think we should be doing more interesting programming. I feel a little awkward playing a program without some sort of connection."

The "connection" is the contemporary nature of the new music he is introducing, pieces by John Adams, Christopher Rouse, Chen Yi, Aaron Jay Kernis and Melinda Wagner. "I would still buy a ticket to hear [Maurizio] Pollini play Schubert, Schumann and Chopin," he says. "But if we can work out a way to make the music of today just as exciting as the music of yesteryear, that bodes well for the future of music. I think there is a lot of really good music being written now."

Not that Ax is abandoning his interpreting of the classics. RCA recently released an album of Chopin's ballades and other works. The Big B's and the Shushes are still in good hands, even as Ax reaches out for something new.