Sir Charles Mackerras, an Australian conductor who played a crucial role in establishing Janacek’s operas in the West; made important discoveries about vocal ornamentation in Mozart operas; and was an elegant conductor of Gilbert and Sullivan’s operettas and Mozart, Mendelssohn and Brahms symphonies, died Wednesday in London, where he lived. He was 84.

His death was announced by his management agency, Askonas Holt of London.

Mackerras was known for performances that were revelatory not only because of their clarity and precision, their astutely judged balances and their consideration of period style, but also because they invariably sounded so deeply felt. He seemed to have an unerring instinct for the right string weights and inflections in Classical and early Romantic works, the right ornaments in Baroque music and the right sense of earthy realism in contemporary scores.

New directions

But his choices were informed by more than instinct. Having grown up hearing Handel, for example, in the fleshed-out re-orchestrations that were common in the 1930s, he made a point of seeking out the original scores and tailoring his own performances to contours that Handel would have found more familiar. An encounter with early performing materials from Mozart operas, which had florid embellishments written into the vocal parts, made him reconsider how Mozart should be performed.

Both those realizations came before detailed research into period style was commonplace, and they occurred early enough in Mackerras’ career to win him considerable attention.

In the case of Handel, a 1959 recording of the “Music for the Royal Fireworks,” using Handel’s original wind scoring — including 26 oboists — was done in a single late-night session and edited and released by the British Pye label within a few days. It quickly became a classic account of the work. The first fruit of Mackerras’ Mozart research was a landmark performance of “The Marriage of Figaro” at the Sadler’s Wells Opera, in 1965.

Alan Charles MacLaurin Mackerras was born in Schenectady, N.Y., to Australian parents, on Nov. 17, 1925, and moved with his family to Sydney, where he was raised. In grammar school he developed an interest in Gilbert and Sullivan operettas, encouraged by his school’s practice of regularly staging productions of the works. Because all the roles (including the female ones) were sung by the school’s boys, he got to know the scores thoroughly.

This knowledge not only helped him become a superb Gilbert and Sullivan conductor but also persuaded him that Sullivan’s music would benefit from arrangement in a popular ballet score, along the lines of “Gaite Parisienne,” Manuel Rosenthal’s suite based on Offenbach themes. Mackerras found an opportunity to create a Sullivan ballet in 1951, when he was commissioned to produce the music for “Pineapple Poll,” a work still performed periodically.

In 1947, having completed his studies at the Sydney Conservatorium and worked as an oboist in the Sydney Symphony, Mackerras moved to London, where he joined the orchestra of the Sadler’s Wells Opera. At Sadler’s Wells he met his wife, Judy, a clarinetist, who survives him, as does a daughter, Catherine. (Another daughter, Fiona, died several years ago.) At Sadler’s Wells, he also met a Czech musician who persuaded him to apply for a scholarship to study conducting in Prague.

His teacher there was the eminent conductor Vaclav Talich, and it was while watching Talich prepare a performance of Janacek’s “Katya Kabanova” that Mackerras found himself “completely and utterly bowled over,” he said in a 2009 interview with Opera Britannia.

Mackerras gave the British premiere of “Katya Kabanova” at Sadler’s Wells in 1951 and helped bring the rest of the composer’s operas to Western houses, where they are now firmly established. He also made a renowned set of Janacek recordings for Decca.

His studies in Prague and his championship of Janacek in London created conducting opportunities for Mackerras in Eastern Europe and Russia.

London debut

His career took off in the West as well. He made his London opera conducting debut with a 1948 production of Johann Strauss’ “Fledermaus.” For his Covent Garden debut, in 1964, he led Shostakovich’s “Katarina Ismailova.” He made his Metropolitan Opera debut leading Gluck’s “Orfeo ed Euridice” in 1972

When Mackerras conducted symphonic works, he painstakingly marked the scores with his preferences about bowings, dynamics and other technical issues, as a way of saving time in rehearsal. The results could be luminous, as his recordings of the Mozart symphonies attest.