Mark Morris is known for taking a fresh, reinvigorating approach to every musical score he selects for his expanding body of work. But with his Romeo & Juliet, On Motifs of Shakespeare, the choreographer has not only envisioned the tale of Shakespeare's youthful, impassioned lovers anew. He worked with a version of Prokofiev's score that had never been publicly performed until Morris' dance had its world premiere last July.

There have been dozens of ballets set to Prokofiev's Romeo and Juliet: one of the most beloved 20th-century scores: since its 1940 premiere at the Kirov Ballet. But that premiere was actually a culmination of five years' worth of political and artistic wrangling that left the composer frustrated and powerless as outside forces distorted his original vision.

The version of the score Leonid Lavrovsky choreographed to in 1940 had undergone considerable alterations from what Prokofiev initially composed in 1935. The tortured history of the score was known, but the original version remained unknown until Prokofiev scholar Simon Morrison, professor of music at Princeton University, discovered the score: a complete piano version, with the composer's instrumentation indicated: as well as a ten-page detailed scenario for the ballet in a Moscow archive.

He brought the score to Morris, whose musical sophistication and sensitivity have long been recognized. Morris seized the opportunity to choreograph to this "new" score. In addition to different orchestral textures and several unfamiliar sections, the major difference from the familiar version is the concluding sections. The lovers do not expire in a tomb; they escape the feudal society with its combative factions, arriving in a separate realm.

After its premiere as part of the Bard SummerScape Festival : as well as performances in California and London : Morris's ambitious production will arrive in New York City as the concluding event in Great Performers' season-long series, "Russian Dreams: The Music of Sergei Prokofiev." Performances take place May 14 _17 at the Rose Theater, with Stefan Asbury conducting the Orchestra of St. Luke's.

Known for his wide-ranging and adventurous musical choices, Morris admits that the Prokofiev score was not one he had previously considered. But taking on the newly discovered version intrigued him. "There's not a lot of radically new music. But it has been reworked and re-thought, from the beginning, back to its origins. Some sections are longer, some are shorter. Sequences and tempi are different. There's more transparency in the orchestration; you hear more percussion and brass and winds, in balance with the strings." Of the familiar version, Morris noted that he "didn't like the massiveness of the score. For me, it was too heavy with strings, and too cinematic."

Morrison made his discovery in the course of researching his book, The People's Artist: Prokofiev's Soviet Years (Oxford University Press). "I knew that Prokofiev had conceived a 'happy-ending' version for the ballet, and that he had worked on some of the music for it. I assumed that, of all of his big Soviet works, this was one that had been thoroughly researched, and there wasn't anything new I could dig up, so I procrastinated with the research on it. When I started probing, the first thing that I came up with was the complete score: the original manuscript, which was not simply abandoned. The 'happy ending' was composed. The instrumentation was largely marked in for that ending."

When the Bolshoi Theatre first commissioned Prokofiev's Romeo and Juliet in 1935, the composer shaped the scenario with Sergey Radlov, an innovative theater director. Artistic and political obstacles intruded before a version of the score, with many changes made over Prokofiev's objections, finally reached the stage. Bolshoi higher-ups objected to the way he had diverged from Shakespeare. Increasingly, Stalinist authorities intruded on the performing arts, imposing their own rigid agendas. The Bolshoi, several of whose leading figures were arrested or dismissed, canceled the production. The Kirov eventually took on the project, but demanded changes in the score's instrumentation and structure to which Prokofiev objected forcefully.

"When I started looking at the political documents surrounding the history of the work, I realized how much controversy was generated by this original version: and how much he fought to have it preserved, and how unhappy he was at the deterioration of the scenario into something that was pretty standard Shakespeare," Morrison says. Prokofiev also had to endure "the simplification of the music: cutting off of the ending, scrapping of some exotic dances, ironing out of some harmonies, and ultimately the thickening of the orchestration. Right up to the 1940 Soviet premiere he really resisted the efforts towards making the work more standard and conservative."

Morris, who uses the title that Prokofiev and Radlov originally intended, creates a rough, tough Verona bristling with youthful energy. His cast of 24: including innovative cross-gender casting of women as Mercutio and Tybalt: offers a focused vibrancy in place of the sheer mass of most ballet productions. "I wanted it to be warmer and dirtier and more crowded. It's a small town. The crowd scenes are very dense and complicated and violent, full of bad relations between clans and between the sexes," the choreographer says. "If you read the play, it's very sexy and very ribald and very strange.

"It isn't the exact same structure as the play; it's 'on motifs of Shakespeare.' I put into it what I thought I needed in order to make the story happen. These are very young people who are in love with one another, and dance in a very simple, young way. It's not an adult romance."

Morrison speaks admiringly of Morris' intricate understanding of the score. "Mark has them dancing to a lot of the odd inner lines of the score, and the strange counterpoint that Prokofiev writes. That weird counterpoint that Prokofiev used is something that thicker orchestrations (and certainly the straightened-out, standard Soviet version) covered up. So he's trying to represent things in the score that are generally not heard."

Prokofiev never had a chance to experience a Romeo with the music and dramatic throughline as he originally intended it. More than seven decades later, Morrison and Morris have provided audiences with that opportunity.