Paul McCartney’s first ballet score, “Ocean’s Kingdom,” is in no way an important addition to the corpus of ballet music, but it deserves a better staging than the one it’s been given by New York City Ballet. Never less than agreeable, it has plenty of color and melody. Curiously, it sounds as if it had been composed in the neo-Romantic era before the Beatles: some of its most expansive tunes have hints of Borodin and Samuel Barber; some of its atmospheres evoke Ravel; and its jolliest passages are on the cusp of Bernstein’s “Candide.”The highlight of Thursday’s gala was the introductory “See the Music ...” session, in which the company’s music director, Fayçal Karoui, spoke about the score, playing excerpts to illustrate several different aspects of Mr. McCartney’s composition: the nature of its melodies; the way it transforms a bass figure through orchestral variation into a theme; its creation of intimacy and humor; its rhythmic urgency and heightened suspense; and, finally, its nobility and optimism. These occasional “See the Music ...” features are a recent development at City Ballet, and a number of the audience members resist them. Yet Thursday’s led us into Mr. McCartney’s music as Peter Martins’s choreography never did.So why was that session the most stimulating part of the evening? We can blame the new ballet’s scenario: it’s trite. We can blame the ballet’s costumes, by Mr. McCartney’s daughter, the fashion designer Stella McCartney: they’re intrusive, unflattering and clichéd. But there have been better ballets to much sillier scenarios, and many of the greatest choreographers (above all, George Balanchine, City Ballet’s founder, with Lincoln Kirstein) have sometimes saddled their work with abysmal costumes.For many people in the audience, it will be enough to say that the choreography was by Mr. Martins. The company’s ballet master in chief since 1983, he has demonstrated more aspects of ballet-making technique than most choreographers will ever learn, and yet for decades now most of his new work has been stale: lacking either felicity of invention or stylistic individuality.Because of Mr. McCartney’s involvement, there was tremendous media excitement about “Ocean’s Kingdom.” And yet I know of no regular balletgoer who felt any great advance hopes for the work; Mr. Martins has turned better music than Mr. McCartney’s into lead many times before now. “Ocean’s Kingdom” isn’t offensive: it’s just harmless, forgettable, bland, thin and occasionally incompetent.In a note for the program, Mr. McCartney writes that he was already working on “a piece of music with an underwater theme” when Mr. Martins invited him to consider a ballet. Mr. McCartney then returned to the underwater idea, now with dance in mind.There is an assortment of characters, some marine, others earthly. Several of Ms. McCartney’s costumes evoke bygone trends from Carnaby Street in London. The entertainers wear luridly iridescent costumes and clownishly fluffy wigs; the aqueous folk (led by Honorata and her papa, King Ocean) wear several layers of filmy drapes in blues and greens of various lengths; the earthly hero, Prince Stone, and his sidekicks have dark dapplings over their torsos, and the odious King Terra (Stone’s brother) and his henchmen, with Mohican-chic hairdos, are dressed in dark colors to remind us of their evil natures.No dancer is made to look any lovelier by this apparel. Sara Mearns, as Honorata, is one of several women whose costumes are cut in a way that makes their upper bodies look heavier above the waist than they are.The ballet, planned like a symphony, is in four movements and is about 50 minutes long. And its problems start at the very beginning, in the scenario described in the program, when it states.“Against the wishes of the lovers (Honorata and Stone), Scala turns back to stop the advancing army and though she is ignored by them, she magically conjures up an intense storm which envelopes and destroys them. To the horror of Honorata and Stone, Scala also perishes. They escape and are met by friendly forces from the Ocean Kingdom. They return home in triumph. ...”Grammar and spelling are not the only problems here: is this a story you need to see played out onstage?Still, nothing is wrong here that some distinguished choreography could not put right. The story is about that prime Romantic subject: lovers from different worlds. So we watch to see the choreography that expresses love’s power to transcend, and it’s here that the ballet disappoints most. Ms. Mearns is America’s most remarkable ballerina today, and Robert Fairchild (Stone) has become City Ballet’s most captivating male dancer, but this ballet does not encourage you to think so. They have a whole series of pas de deux — at least one in each of the four movements — and yet these each prove only so much blah.When they express mutual delight, they take turns propelling each other around; when they are frustrated and unhappy, he supports her in backbends. Every situation finds them stuck in an emotional rut. Mr. Martins doesn’t rise to the music’s big melodies with any sustained dance idea, and he doesn’t bring its liveliest rhythms to life with any eye-catching metric complexity. I hope someone else choreographs this score before long: it has many more dance opportunities — especially in its finale — than Mr. Martins has chosen to realize.If you read the synopsis only afterward — as I did — you find that it clears up a number of points that were unclear onstage. Georgina Pazcoguin makes a dramatic impression throughout the action as Scala, an initially sinister character in charge of Honorata’s handmaidens, but it’s hard to tell why Scala is involved in the first place, what her motives are for changing her mind, or even that she eventually perishes.When introducing his company’s galas from the stage, Mr. Martins’s favorite gimmick is to make a toast and tell the audience that this house tradition was started by Balanchine. Plenty of people know perfectly well that Balanchine originally said, “In Russia we drink the health of the guy that died” before tossing some vodka down the hatch by way of hailing his friend Stravinsky, but never mind: it’s always an event to watch Mr. Martins having a snifter as he hails some benefactor (usually alive these days) or another. On Thursday he toasted Mr. McCartney with a cup of tea.