This group plays music the way we hum a nursery rhyme

For contemporary music fans, the highlight of the ''Britain Salutes New York 1983'' festival had to have been the three-night visit of Peter Maxwell Davies's unique group The Fires of London.

''Fires'' was set up to perform Davies's music, and of late they have been branching out to play some of Elliott Carter's music as well. I caught up with two Davies works and a brand new Carter.

''Le Jongleur de Notre Dame'' tells the traditional French tale of a juggler-turned-monk who lacks the skills of his brethren, but his simple gift of juggling is accepted by a statue of the Madonna, while the more eloquent praise of the others is rejected.

Davies gives the brothers voices of instruments. The Abbot sings, and the Juggler juggles. It is a childlike story, told in a simple manner that somehow sounded lackluster from the composer of ''Eight Songs for a Mad King'' or ''Miss Donnithorne's Maggot.''

In fact, ''Eight Songs,'' which closed the first program, remains a crowning achievement - a virtuoso theater piece that ideally weds music to theater to song. Each player has a pivotal role in the piece, though Michael Rippon emerges as the dazzling star of the piece - as Mad King George.

Mr. Carter's ''Triple-Duo'' is a 21-minute Carterian exploration of the sonoric possibilities of three sets of two instruments each - flute-clarinet, violin-cello, piano-percussion. As with most of Mr. Carter's music, first hearings reveal little more than thorniness and complexity.

The Fires musicians - Philippa Davies (flutes), David Campbell (clarinets), Rosemary Furniss (violin-viola), Jonathan Williams (cello), Stephen Pruslin (keyboard instruments), Gregory Knowles (percussion) - are virtuosos all and form an astounding group of talent. They play Davies the way we hum nursery tunes, and hearing them perform this music is a special experience. London Symphony

The London Symphony Orchestra paid New York's two major concert halls one visit each last week, also as part of ''Britain Salutes New York.'' It no longer sounds like the warm, glowing ensemble that used to visit these shores when Andre Previn was its chief. Claudio Abbado has a harder ear, and the orchestra sounds glassier, edgier, sterner. In fact, the orchestra sounded downright unfriendly in Avery Fisher Hall, a place that emphasizes the most unpleasant qualities of any orchestra that performs there.

The Webern ''Six Pieces'' that opened the program went for naught for the audience noise that drowned most of the performance out. Stravinsky's ''Firebird Suite'' received an analytic, chilled account that refused to revel in any beauty of texture. Mahler's First had grand proportions, an amazing seriousness (even when wit and irony were called for) and an explosive grandeur that packed a certain punch.

At Carnegie Hall, the orchestra sounded happier, a bit warmer, and thrillingly virtuosic. But again, a chilliness pervaded the air. Elgar's brooding, haunting Cello Concerto was given a dispassionate performance from both masetro and the rich-toned cellist, Antonio Meneses. Berlioz's ''Symphonie Fantas-tique'' was laced with virtuosic relish, but any attempt at capturing Berlioz's visions of love, death, and pandemon-ium was not evident.

The orchestra proved itself to be a dazzling ensemble. Mr. Abbado, however, proved himself to be in a disturbing new phase of his career that seems to put calculation over emotion, intellect over heart. It bears no resemblance to those qualities he used to bring to his work that made him such a special talent. Berlioz's daring opera

With his Benvenuto Cellini, Hector Berlioz had hoped to establish himself as an eminent opera composer. His bid failed, the work failed, and it has had a checkered performance career ever since.

It is a daring piece - full of tricky ensembles, rapid-fire duets, trios, sextets, elaborate arias that demand much of the singers without the overt rewards of instantly hummable melodies. It has none of the earmarks of instant success, but to sit through the entire opera - either in concert or in an opera house - is to be awed by Berlioz's vision, by the daring of his ideas, by the genius that allowed him to execute his visions with staggering imagination and ingenuity.

Sarah Caldwell mounted the opera in Boston for Jon Vickers in the mid '70s, and though flawed, her production proved that the work can be riveting on a stage. The work's strengths were proven anew in Eve Queler's performance at Carnegie Hall Sunday evening, with her Opera Orchestra of New York forces. (The entire ''show'' moves to the Kennedy Center in Washington this Saturday evening, for the delectation of any lover of good opera, of Berlioz, and of remarkable singing.)

Miss Queler serves a vital need in the artistic fabric of New York. Her conducting gifts are not stellar, but she has the fervor of a real believer, and in just about everything she does, the result is a fair asessment of the work at hand. Berlioz's is a unique musical idiom, and at times she did not entirely comunicate the extent of that uniqueness. But the orchestra played handsomely, the chorus sang ardently, and Berlioz emerged heroically.

The cast assembled seemed uniformly stronger than the Opera Orchestra norm, from the lesser roles, through the pert Ascanio of Brena Boozer, right on up through the principal cast. Donald Gramm sang an imposing Pope Clement VII, Cellini's patron. Jean-Philippe Lafont and Marc Vento, both from Toulouse, France, made strong impressions as the clownish Fieramosca and as Balducci, respectively. Mariella Devia gave a rich-voiced, gossamer-toned account of Teresa, proving yet again that she is the most important lyric-coloratura of her generation.

But the evening belonged to Nicolai Gedda. Gedda blooms in opera, which is why the Met's half-hearted piano-voice recital to honor his 25th anniversary with that company was so dispiriting. His voice takes on a freshness, a resilience, a strength with an orchestra. Cellini is one of Gedda's finest roles , and this veteran tenor's demonstration of the art of great singing was a particular treat for all assembled. Thanks to Miss Queler for letting New Yorkers cheer him the way he deserves in this milestone year of his career.