By Anne Midgette
Washington Post Staff Writer
Saturday, February 27, 2010; C03

It isn't only new-music specialists who can be creative, even inventive, onstage. Robert Levin, a musicologist and pianist specializing in historically informed performance (sometimes known by the abbreviation HIP), gave a performance of Beethoven's First Piano Concerto with the Baltimore Symphony Orchestra on Thursday night that was so filled with improvisatory touches, it sounded almost like a new piece.

Improvisation was long a vital part of the Classical music tradition: a staple of the performances of Mozart, Beethoven, Chopin and others, to say nothing of opera, which singers routinely embellished with passages sung off-the-cuff. Yet for years, particularly since the advent of recording, it almost entirely ceased to figure in the Classical music performance tradition; conservatory students are taught to follow the letter of the score.

Improvisation has been relegated to the field of jazz. That's changing, slightly, as artists such as John Bayless and Gabriela Montero try to fold the jazz tradition back into the Classical world. And in the field of historically informed performance, it's often the most knowledgeable performers who have embraced improvisation most ardently, like Levin, or the conductor René Jacobs, whose Mozart and Handel recordings are full of all manner of interpolations (check out his "Don Giovanni").

And on Thursday, Levin, who has done pioneering work in establishing the way that Mozart's and Beethoven's music actually sounded in their day, not only improvised all of the cadenzas ("Pray for me," he told the audience), but offered, after the intermission, a Fantasy in Beethoven's style, based on four snippets of music submitted to him by the audience. Given fears that musical illiteracy is rampant among the general population, it was heartening to see that enough audience members were able to write out a few measures of musical notation to partly fill a wicker basket, though one of the snippets Levin chose on Thursday came from the conductor, Nicholas McGegan.

The improvised Fantasy was an impressive feat, but the Beethoven concerto was more revelatory. It underlined the difference between live performance and the entombed perfection of a recording: Levin's reading was in and for the moment, with plenty of touches you might not want to have held up as a definitive interpretation, but that added considerable vigor to the immediate experience.

Playing on a modern piano, with a modern orchestra, Levin wasn't aiming for literal authenticity, but for the flavor of 19th-century performance. His left hand brought out an emphatic, regular bass line while the right hand danced above it; his tempos slowed and sped up with a license that by today's standards was positively radical; he played along with the orchestra in passages when the piano is normally quiet. The only feature that sounded anachronistic, at least with this instrument, was the heavy use of pedal.

Levin was enlightening, but it was McGegan who gave the evening musical warmth. McGegan is one of the leading period-performance conductors in the world: the artistic director of the venerable Handel Festival in Göttingen, Germany, and the music director of the Philharmonia Baroque Orchestra in San Francisco.

On Thursday, he showed that he'd earned his credentials, leading the BSO in readings of Mozart that found a sense of lightness, a spring to their step, without being self-conscious or restrained in their attempts to find the proper style. The "Marriage of Figaro" Overture was sinuous from the opening measures, which the violins played in a single stroke of the bow. And the "Jupiter" Symphony, played with every last repeat, was offered with ebullience: the third movement audibly swaying, like a body moved by the infectious dance meter; the fourth leaping up with that peculiarly Mozartean exuberance. On paper, it looked like a program of standards. In person, though, the concert was HIP indeed.

The program repeats Saturday at 8 p.m. at Strathmore.