Historically informed performance has come a long way since the early 1980s, when conductor Neville Marriner mocked its proponents as “the open-toed sandals and brown bread set.” As one of the most noteworthy developments in classical music performance over the last few decades, the historical performance movement has yielded fresh interpretations of familiar repertoire, brought neglected works of merit back into active circulation, encouraged a deeper exploration of issues regarding musical style, and forged a closer bond between musicology and performance.

No artist has done more to bring the movement credibility than esteemed conductor, harpsichordist, and flutist Nicholas McGegan, who conducts the Juilliard Orchestra in its first concert of the season on October 2 in the Peter Jay Sharp Theater. While McGegan, sees the performance as a valuable opportunity to familiarize young players with a historically informed approach, his principal goal, he says, is simply “to have a good time and entertain the audience. After all, if we don’t bring joy to our music making, what’s the point?”

Known for his astute and exuberant musicianship, the 58-year-old maestro has served as music director of San Francisco’s Philharmonia Baroque Orchestra, the country’s leading period-instrument orchestra, since 1985. (The group also performs Classical and early-Romantic music, as well as contemporary works on occasion.) McGegan has made more than 30 recordings with the P.B.O., including the award-winning premiere recording of Handel’s Susanna.

As noted in The New Grove Dictionary of Music and Musicians, McGegan’s career has been “inextricably linked to the resurgence of interest in Handel’s music, of which he is a renowned champion.” He has recorded more Handel operas than anyone else and has been music director of the Göttingen Handel Festival, the world’s longest-standing early music festival, since 1990.

Born in England, McGegan entered Cambridge University with the intention to study contemporary music and composition, but his interests shifted after his acoustics professor loaned him an 18th-century flute and he became friends with the professor’s tenant, harpsichordist and conductor Christopher Hogwood. After joining Hogwood’s Academy of Ancient Music as a flute player in the early 1970s, McGegan went on to further study at Oxford. At the time, as McGegan recalls in an interview with Don Kaplan published on www.mustcreate.org, Baroque music was hardly fashionable: “Nobody performed it, and certainly nobody recorded it, except those dismal old Archiv records that were rather like bran muffins that were too good for you.”

McGegan is one of the foremost musicians who have vanquished that outmoded approach with his inspired interpretations of Baroque and post-Baroque repertoire. Indeed, the long history of compelling performances and lack of dogmatism evidenced by McGegan and many of his peers have undoubtedly contributed to the increasing interest in historically informed performance by American orchestras. Today, McGegan not only performs with the Philharmonia Baroque Orchestra and Arcadian Ensemble (a chamber music offshoot of the group), but routinely conducts leading modern orchestras throughout Europe and the U.S.: in fall 2008 alone, he is scheduled to conduct the Cleveland, Atlanta, St. Louis, Chicago, Milwaukee, San Diego, and Nashville symphony orchestras.

But how does McGegan go about achieving a historically informed performance when conducting a modern orchestra? As he explains, there’s much more to historical performance than just using original instruments. Bowing conventions, for instance, were considerably different in earlier eras, with the Baroque style producing more of a “bouncy” feel. “I always travel with my own instrumental parts with the bowings marked so that we don’t waste time during rehearsal,” McGegan said in a telephone interview.

Another notable difference is a significant reduction in the number of string players. For his program at Juilliard—which features Handel’s Concerto Grosso in B-flat Major, Op. 3, No. 2; Haydn’s Symphony No. 104 in D Major (“London”); Mozart’s Piano Concerto No. 15 in B-flat Major, K. 450; and Prokofiev’s Symphony No. 1 in D Major (“Classical”)—McGegan will rotate players so that no more than 20 violinists play in any given piece. (McGegan’s Philharmonia Baroque Orchestra includes 18 violinists, while modern orchestras typically have more than 30.) He also plans to employ a historical seating arrangement, with the first and second violins on opposite sides of the stage. For the Mozart piano concerto, he hopes to have the piano in the center rather than in front of the orchestra, “provided the soloist is amenable.” Even with seating arrangements, however, historical accuracy can be elusive. “For the Haydn,” as McGegan points out, “we know what the seating arrangement at the first performance was, but we won’t be able to reproduce it exactly, since it utilized curved risers.”

As for Juilliard’s plans for a graduate-level program in historical performance beginning in fall 2009, McGegan praises the decision as “absolutely wonderful,” noting that such a program, “provided it is integrated fully into the curriculum rather than remaining on the sidelines, will be tremendously valuable to future orchestral musicians—it will serve as another ‘string in their bow,’ so to speak.” Although he is entirely too tactful to use the word “overdue” in connection with the impending program, he does note that such programs have existed for considerably longer in Europe; McGegan himself served as head of the early music program at London’s Royal College of Music for several years in the early 1970s. Given the preponderance of Juilliard alumni in leading orchestras, it is also revealing that McGegan’s Philharmonia Baroque Orchestra includes just one Juilliard graduate: cellist David Goldblatt, who studied Baroque cello in Amsterdam after completing his M.M. at the School.

For McGegan, though, the most important measure of authenticity isn’t the use of original instruments or adherence to a particular set of conventions, but the emotional impact of the performance. As he told an interviewer before a performance of Handel’s Messiah with the New York Philharmonic and Westminster Choir (www.nyphil.org), “There is an authenticity that exists in a performance, and that is ‘Does it get its message across?’ It has nothing to do with what edition you used, whether you played period instruments, or engaged a countertenor instead of an alto. In other words, was the audience moved by that performance? Did Handel pluck your heartstrings? If the answer to that is ‘yes,’ we did well.”