NEW YORK, NY.- In 1916, composer Gustav Holst took a young conductor, Adrian Boult, on a long walk through Kew Gardens and Richmond Park in London. A few years earlier, Boult had written to Holst asking whether he had composed any music for small orchestra that he could perform. On this day, though, they discussed a much grander prospect: a suite for large orchestra that would become “The Planets.”

Holst arranged for Boult to hear a version of the piece at the piano, played by two of his colleagues, Vally Lasker and Nora Day. Few were better equipped than they were to introduce Boult to the score; as rehearsal pianists, amanuenses, copyists and performers, the two would be intimately involved in the creation of “The Planets,” one of the most popular orchestral pieces of the 20th century.

Documents from Lasker’s archive at the Royal College of Music in London show that this way of introducing “The Planets” to other artists wasn’t so unusual in its genesis. In an introduction to the piece given by Lasker on BBC radio in 1951, she said, “We had the great joy of introducing the work to all the great conductors in this country, and, after the war, to many of the great continental conductors.”

Karl Straube, Paul von Klenau and Wilhelm Furtwängler were among the international figures who heard early versions of “The Planets” played by Lasker and Day. The pair also helped Boult get up to speed as he agreed at short notice to conduct the work’s premiere to selected guests in 1918.

In January 1920, Lasker and Day played “The Planets” for Ralph Vaughan Williams, Holst’s friend and close musical associate, and by the time the work received its full public premiere later that year, by Albert Coates and the London Symphony Orchestra, the music already had many important admirers.

As the world of classical music observes the 150th anniversary of Holst’s birth this year, “The Planets” bears revisiting. If there’s a single work that dominates our understanding of him, it’s this colorful, exciting, slightly eccentric orchestral suite.

It originally had the working title Seven Pieces for Large Orchestra, which Holst biographer Michael Short links to Arnold Schoenberg’s color-driven Five Pieces for Orchestra. The planetary titles came later. But, as Lasker noted, they were derived not from mythology, but from astrology, which Holst had been introduced to in 1913, on a visit to the Spanish island of Mallorca, with writer Clifford Bax and his composer brother, Arnold. Each movement describes a planet’s astrological character: “Mars” is the bringer of war; “Neptune,” the mystic; “Saturn,” the bringer of old age.

“The Planets” has grown only more popular with time, on a journey from orchestral programming staple (featured at the BBC Proms 88 times since its first performance there in 1921) to cultural touchstone (influencing composers like John Williams, whose “Star Wars” soundtrack bears its mark) to civic emblem in Britain.

Cecil Spring Rice, a British diplomat and poet, added a lyric to the slow theme from “Jupiter”; the result, “I Vow to Thee My Country,” became a stirring national hymn to rival Hubert Parry’s “Jerusalem” or Edward Elgar’s “Land of Hope and Glory,” and was featured at the funerals of Winston Churchill, Diana, Princess of Wales, and Margaret Thatcher.

“The Planets” was composed and orchestrated between 1914 and 1917, and was first performed for the public in 1920. During that six-year period, Holst relied heavily on a group of supportive women whom he later referred to in the dedication to his opera “At the Boar’s Head” as “my scribes.”

Holst was a busy musician when he began to think about “The Planets.” In addition to composing, he juggled work at three institutions: Morley College, James Allen’s Girls’ School and St. Paul’s Girls’ School. He formed a strong attachment to those places, and his catalog reflects that, in pieces like “Brook Green Suite,” written for St. Paul’s junior orchestra while he was hospitalized toward the end of his life and titled after the school’s location in Brook Green, Hammersmith.

His activities were complicated by lifelong bad health. In particular, Holst had suffered since childhood from neuritis in his hands, first affecting his ability to play the piano — he later opted for the trombone — and later making him struggle with the more laborious aspects of composing. Those included copying, part-writing and orchestration, tasks that, in a time before digital engraving or photocopying, required “a huge amount of physical effort, and that took an awful lot of time,” music historian Leah Broad said in an interview.

Despite health complications, Holst gained a reputation as an enthusiastic multitasker, with a passion for large, ambitious performances. In 1911, while he was the music director at Morley College, he headed up large revivals of Henry Purcell’s music, with works like “King Arthur,” “Dioclesian” and “The Fairy Queen” being heard for the first time in hundreds of years.

Holst did find a solution to his competing ambition and physical incapability, and he left traces of it on the cover of the 1911 “Fairy Queen” program, which lists 28 copyists who worked for 18 months to copy some 1,500 pages of parts. “The Planets” was similarly bold, especially as a project undertaken during wartime. His pupil Jane Joseph commented that he “resigned himself to needing a vast orchestra which no one would be able to afford in wartime.”

To help with the preparation of “The Planets,” Holst enlisted Joseph, as well as Lasker and Day, who were both music teachers at St. Paul’s, to act as his amanuenses. Because the neuritis affected his writing hand in particular, Holst once described the women as his “three right hands”; Imogen Holst, the composer’s daughter, described their role in completing the 198 pages of the full score as “invaluable.”

There was no free time during the school week, so the writing of “The Planets” took place on weekends, with activity centered around the new, soundproof music room at St. Paul’s. (The space is still used as a music room today, with a placard that says “Mr. Holst’s Room” on the door.) Holst, seated away from the piano, would ask them to try out material, dictate parts of the score or give orchestrational directions.

Some idea of what that environment was like can be found in a memoir Lasker wrote for the school magazine, Paulina, in 1960:

“He had his piano sketch, and with red ink, he wrote against each note which instrument played it. In another room, Jane Joseph, one of his pupils, worked on a different part of the score. As soon as she and Nora Day had done four pages — we were all working in the same building — they brought them to me in another room and I transcribed it for the piano. In six weeks we had done the whole lot. We all worked eight hours a day and I can’t imagine any other composer working in this way without any worry or loss of temper.”

Sections of the “Planets” manuscript are available online via the Royal College of Music’s archives, and they clearly show a similar collaborative process in action. Written on the two-piano score in red ink are Holst’s instructions for orchestration; elsewhere, there are large sections crossed out and notes in margins about whose handwriting is whose and where that changes.

In 2009, Holst scholar Alan Gibbs compiled a list of all of Lasker’s arrangements, for Holst and others. Included are multiple arrangements of “The Planets,” vocal scores of Holst’s operas “The Perfect Fool” and “At the Boar’s Head,” and amanuensis work on his “Japanese Suite.” There are also details of the similar relationship Lasker and Day had with Ralph Vaughan Williams, with arrangements for piano of his “London,” “Pastoral” and Fourth Symphonies, as well as his ballet “Job” and his Piano Concerto. These were made for a variety of purposes: rehearsals, demonstrations, performances, as a sounding board for ideas, as a way to persuade conductors to champion the work.

“We have very strong conceptual models for thinking about solo authorship and solo genius — this kind of outpouring of genius, from one person, from their perspective,” said Broad, the historian, adding that “we don’t have as developed a way of thinking about collaborative creativity.”

In the case of Holst, there never seemed to be any doubt in the group about the identity of the “Planets” creator, nor about the composer’s appreciation for those he worked with. He later dedicated pieces to Lasker, Day and Joseph, who wrote that Holst “is indisputably master, and no less indisputably comrade.”

But perhaps this might be reflected better in our understanding of “The Planets,” given how famous it is. On the exterior of St. Paul’s there is a blue plaque issued by English Heritage. It reads: “Gustav Holst (1874-1934) wrote ‘The Planets’ and taught here.” To that, we might now add “with help.”

This article originally appeared in The New York Times.