Experiencing Brahms : Roger Norrington and the L.A. Philharmonic will take a close look at composer’s symphonies.

Roger Norrington is a self-described crusader, a conductor on a mission. His passion is the pursuit of authenticity--rediscovering and performing great classical works as closely as possible to the way they were originally composed and played.

Delving into music history, from tone to technique, he has produced performances that, to say the least, surprise the ear attuned to the sounds of modern instruments. Authentic 18th and 19th century music played by period orchestras is for the most part softer, more expressive, often lighter in sound than the reverential, grandiose, sonority of modern orchestras.

“Classical music was often deeply irreverent,” Norrington points out, alluding particularly to Mozart’s comic operas or even Haydn symphonies.

During a break in a recent Schumann rehearsal with the London Philharmonic, Norrington, 63, compares the effect with looking at a newly cleaned painting. When the restoration of Rubens’ “Lady in a Straw Hat” was first displayed in the National Gallery, he says, “There was a terrible outcry that there were these rather horrible colors . . . like the Sistine Chapel today.”

And so music’s original colors are his goal. Of contemporary playing, Norrington says: “So much of it is irrelevant. If you play everything like Wagner, including Bach and Mozart, of course it changes the music immensely. Each composer has his own sound and each his own historical perspective.”

To help audiences back to an 18th or 19th century mind-set, Norrington has devised his own crash courses, which he calls Experiences. Over one day or a weekend, with a little help from orchestras and musical colleagues, he explains and leads performances, rehearsals and discussions of one work or a set of works by one composer.

In Los Angeles this weekend, he will unveil his Brahms Experience. With the Los Angeles Philharmonic, he’ll focus on all four Brahms symphonies via open rehearsals, pre-concert talks, related recitals, lectures and annotated performances, all through Saturday and Sunday. A shorter program will be repeated next Wednesday.

Norrington started his pioneering crusade when he began researching music by the likes of Cherubini, Monteverdi, Lully and other 17th century musicians. “There wasn’t a way in which great conductors played Monteverdi, because they just didn’t play it at all,” he says. “The thing about this kind of music is that you’re forced to be creative.”

Original instruments were the first step in learning how to play the scores. “They show you the way,” he says, telling of his search for “funny things like the cornettino. . . . People would ring up and say, ‘I’ve got a chitarrone, or a baroque violin.’ ”

One composer’s work led to the next. “I think I conducted the world’s first Handel’s Messiah with original instruments . . . then I wondered how Haydn would sound, and Mozart, Beethoven and Brahms,” the conductor says.

In every case, Norrington re-read the music in the context of the composer’s life and times. He explains: “It’s like reading Jane Austen: It doesn’t mean what you think it means today. ‘Sense and Sensibility’ doesn’t mean, ‘Now be sensible, dear,’ it means the opposite, ‘Be sensitive, my dear.’ ”

At the Brahms Experience, the backstory will definitely be part of the show. “I think you can trace Brahms’ life through his music, and that’s what I plan to do,” Norrington says.

In a short introduction before the concerts, he will explain “a sort of mission guideline--your mission is to hear the following. Of course, there could be 10 different ways of listening but the important thing is to feel the music--it’s not just chords, instruments making nice noises.”

Brahms’ emotional life story is a concealed one, he warns. Unlike Tchaikovsky, who wore his heart on his sleeve musically, Brahms’ turbulence hides under “a formidable technique.” As British composer William Walton once said, “You can’t write a big thing like a symphony unless something terrible has happened to you.” Brahms was shy, reticent and unhappy. He fell hopelessly in love with Clara, the wife of his beloved friend and guru, composer Robert Schumann, and he watched helplessly as Schumann slipped into madness and a tormented death.

The music is a release. “Brahms could just say, ‘It’s just music,’ but it’s not. It’s all about him and Clara and Robert and being alone,” Norrington points out.

Today, Brahms would recognize the instruments in a modern orchestra but not its size and makeup. With the thoroughly modern Philharmonic, authenticity calls for some rearrangement. Under Norrington’s direction, at each concert performance, the orchestra will divide into two different-sized orchestras. For Symphonies Nos. 2 and 3, the configuration will be “the normal Brahms-sized orchestra of 12 first violins,” Norrington says, instead of the usual 14. All the string forces will be similarly reduced.

Then, for the First and Fourth symphonies, Norrington will use “a modern, big orchestra . . . with double woodwinds--16 instead of eight. In the 19th century, they doubled woodwinds when they had a lot of strings. It’s the proportion that really matters rather than the numbers.”

And Norrington’s placement of the players will also match 19th century style. The first- and second-violins face each other rather than sit side-by-side, making for a more pervasive, amalgamated sound.

In the 30 years since Norrington started his crusade, such manipulations in pursuit of authenticity have become almost commonplace. It’s just one sign that the persevering pioneer has moved from the fringes to the mainstream in the music world.

Brahms--and More Brahms

SATURDAY

10 a.m.: Open rehearsal, Brahms’ Symphony No. 3, Symphony No. 4

2:30 p.m.: “An Introduction to Brahms,” lecture by Michael Steinberg

3:30 p.m.: Brahms’ song recital, Gundula Janowitz, soprano; Grant Gershon, pianist

7 p.m.: Pre-concert discussion, Roger Norrington and Michael Steinberg, pre-concert discussion

8 p.m.: Concert: Brahms’ Symphony No. 1, Symphony No. 2

SUNDAY

10:30 a.m.: Complimentary coffee and croissants

11 a.m.: “Exploring Brahms’ Chamber Music,” lecture by Michael Steinberg

11:30 a.m.: String Quintet in G, Opus 111, members of the L.A. Philharmonic

1:30 p.m.: Pre-concert discussion, Roger Norrington and Michael Steinberg

2:30 p.m.: Concert: Brahms’ Symphony No. 3, Symphony No. 4

* Dorothy Chandler Pavilion, 135 N. Grand Ave., each symphony concert and pre-concert discussion, $4.75-$63; other Experience events, Saturday, $5-$20; Sunday, $5-$15. Experience ticket-holders entitled to a 20% discount at Otto’s Bar and Grill at the Music Center, for lunch and dinner. (213) 850-2000.