MUSIC REVIEWS : PHILHARMONIA BAROQUE AT AMBASSADOR

Philharmonia Baroque Orchestra laid claim to being America’s premier period-instrument ensemble when it performed music of Handel here last month under its brilliant new music director and conductor, Nicholas McGegan.

On Sunday, the ensemble returned to confirm that favorable impression in a mostly Mozart program at Ambassador Auditorium. The Bay Area group was deputizing for the English Baroque Soloists, whose American tour had run out of financial steam on the East Coast.

In playing Mozart for the first time in its young life, Philharmonia was doubtless inspired by the soloist of the evening, Malcolm Bilson, whose fervent advocacy and lively, stylish interpretations have helped bring the fortepiano from near-oblivion to a central position in the current, unprecedentedly intensive reexamination of 18th-Century performance practice.

Conductor McGegan, his orchestra and the pianist worked together like old comrades in two contrasting Mozart concertos: the blithely urbane A-major, K. 414, and the ever-astonishing Concerto in E-flat, K. 271, with its surges of high drama and somber passion amid the galant gestures.

In both works, Bilson played with his customary vigor and technical aplomb, presenting, in the wonderfully deep, rich slow movement of K. 271 a master lesson in rhythmic freedom heightening expressivity.

Throughout the program, McGegan’s incisive conducting communicated a remarkable degree of emotional tension and dynamic variety within the context of the gentle sonority of Philharmonia’s gut strings, sweetly reedy oboes and slightly buzzy valveless horns.

In addition to the concertos, the program offered a fittingly propulsive, if roughly executed, reading of Mozart’s bleak Adagio and Fugue in C minor for strings and a flawlessly executed Overture to “La Calamita de’ cuori” of Johann Christian Bach, from which Mozart swiped a theme for the slow movement of his A-major Piano Concerto (which appeared next on the program), in the process elevating a morsel of period fluff to music of timeless greatness.