London — To many dance lovers, ''Giselle'' is the ''Hamlet'' of the ballet world. Often described as the perfect classical ballet, the interpretations of its title role are as closely studied as performances of Shakespeare's ill-fated Prince of Denmark.
It is one of those leading roles that tests a dancer's abilities and talents. And it can turn a ballerina into a star.
The ballet is short with just two acts, compared with the prologues and four acts of its sister favorites - ''Swan Lake'' and ''Sleeping Beauty,'' whose evenings can last 41/2 hours. It offers innocence and purity in lyrical dancing, beautifully memorable music by Adolphe Adam, a sense of mystical magic in a moonlit wood, and a simple story that appeals to all ages.
Giselle, a pretty peasant girl, is deceived in love and dies of a broken heart. As a phantom, she goes on to save her now-repentant, still-mourning lover from death at the hands of the wilis - the ghosts of betrothed girls who died before their wedding days and who rise from their graves at midnight to dance to death any man they encounter.
The ballet is as popular now as it was when first produced in Paris in 1841. With the fabled Carlotta Grisi as Giselle, it became an immediate success.
Today, Giselle's balletic steps and movements are found worldwide. But how does each dancer make the role uniquely her own?
For Margaret Barbieri, a principal with the Sadler's Wells Royal Ballet, a recent performance also marked the one-hundredth time she herself had appeared in the role. She summed it up to me by quoting from Konstantin Stanislavsky: ''Don't act the role - you must be the role.''
''This ballet has so much to offer,'' she said. ''It's challenging and demanding. I see Giselle as a highly strung girl - very sensitive, excitable.
''She gives everything to Albrecht, and it is the end of her world to discover him unfaithful to her promises. Each time I perform it I try to refine the role, hopefully finding more in it and letting it come out spontaneously.
''And people are always moved by a story of unrequited love. . . .''
Another view of ''Giselle'' as a ballet comes from the director and prima ballerina of the National Ballet of Cuba, Alicia Alonso (whose Giselle I saw at the Bolshoi in Moscow when she was almost 60 years old and whose dancing in Act II still seemed completely weightless).
She calls the ballet ''the most beautiful . . . I had ever seen.'' In a detailed interview about Giselle in Barbara Newman's book ''Striking a Balance, '' Miss Alonso tells how she put hours of study into the role, learned everyone's parts, male and female, and could dance the whole ballet in her head with all the exits and entrances.
She read ''everything about the Romantic era, looking at the lithographs and critics of that time. . . . The background material gives you richness to understand the part . . . so you can portray the style and believe in what you are dancing.''
Another Giselle - Evelyn Hart - is a pert and delightful young Canadian dancer. To me, she laughingly admitted that she had done no deep research into the role's background. Yet ''I become Giselle. . . . I feel the part,'' she told me the day after she had performed ''Giselle'' as a guest with the Sadler's Wells Royal Ballet.
She was acclaimed by veteran London critic Clement Crisp as a ''born Giselle whose interpretation is clear in focus, luminous in its romantic sensibility, and unerring in taste.''
To Miss Hart, Giselle is ''first and foremost a believable character. I've seen a lot of performances and have been disappointed by Giselle's first entrance. She is seen as gentle, so in control, a sweet young thing. . . . Well, if so, how does she later go mad?
''To me she is a peasant, loves life, probably always has been frail, and therefore doesn't pay attention to it. She shows extreme emotion, so when she is mad it makes sense. . . .
''She simply delights in love. I try to feel totally in love with Albrecht, which results in total devastation when he claims Berthilde (his real fiancee). . . .
''Now, Act II is something else. She's like a guardian angel watching over him. . . . It's painful for her to see what he is going through. . . . That is why I don't dance with the blank face as most dancers do. . . .
''She tries to make contact with him, come close to him. It's the strength of love that develops the point of contact. Just when he thinks he has her back, she fades away. But at the end he comes to terms with his love for her. . . .'
Miss Hart's natural ability to understand the role of Giselle is emphasized in her beautiful, flowing dancing.
''Giselle is many-faceted. . . . Everyone can relate to it, and that's why it has lasted so long,'' Miss Hart concluded.