This is the breakthrough work of Edward Elgar, a national composer of England known for pieces like "Salut d'Amour" and "Pomp and Circumstance." The original work is an orchestral piece consisting of a theme and 14 variations. The piano solo version was arranged by Elgar himself.

This piece was written in 1898, when Elgar was in his 40s, and premiered the following year in 1899 under the baton of Hans Richter, achieving great success. This success brought Elgar international fame and served as a stepping stone to the subsequent triumph of "Pomp and Circumstance."

The official title of the piece is "Variations on an Original Theme," but because "Enigma" was printed on the first page of the score, it also came to be known as "Enigma Variations." "Enigma" is a Greek word meaning "riddle," "puzzle," or "conundrum."

What was the "mystery" Elgar embedded in this piece? Elgar is said to have hidden two "mysteries" in these variations. The first mystery lies in the initials given to each variation. Elgar assigned nicknames or initials of his friends to the 14 variations, writing music that expressed their individual personalities. Elgar, stating it was "personal," did not reveal the full names, leaving them as a mystery, and dedicated the piece to these 14 enigmatic friends.

The details and deciphering of the theme and the 14 variations are as follows:

Theme "Enigma" Andante, 4/4 time, ternary form. The A section, up to the first six measures, is in G minor, followed by the B section of four measures in the parallel key of G major. From measure 11, it returns to the A section and G minor.

Variation 1 "C.A.E" L'istesso tempo, 4/4 time, G minor. A romantic and delicate variation. These initials refer to Caroline Alice Elgar, Elgar's beloved wife, who devotedly supported him throughout his life. The famous "Salut d'Amour" was Elgar's proposal gift to his wife Alice, and depicting his wife at the beginning of the variation well reflects Elgar's character as a devoted husband. The figure including triplets comes from the whistle Elgar used to blow when returning home.

Variation 2 "H.D.S-P" Allegro, 3/8 time, G minor. A piece named after Hew David Steuart-Powell, a pianist friend with whom Elgar enjoyed playing chamber music. The rhythmic and powerful melody comes from his piano finger exercises.

Variation 3 "R.B.T" Allegretto, 3/8 time, G minor. A piece named after the eccentric actor Richard Baxter Townsent. As if representing a person who could produce a wide range of voices, from low to high soprano-like tones, the piece has a wide range of notes and is rich in the low register characteristic of a male voice.

Variation 4 "W.M.B" Allegro di molto, 3/4 time, G minor. A piece named after William Meath Baker, a landowner and scholar from Elgar's hometown of Worcestershire. A vigorous piece that well expresses the temperament of this energetic gentleman who loved Wagner.

Variation 5 "R.P.A" Moderato, 12/8 time, C minor. A piece named after Richard P. Arnold, son of the poet Matthew Arnold, and a scholar and pianist. He was a sensitive person, and the musical character combines seriousness and wit.

Variation 6 "Ysobell" Andantino, 3/2 time, C major. The nickname of Isabel Fitton, Elgar's violin student (who later switched to viola). The motif is a viola passage depicting the practice of crossing strings.

Variation 7 "Troyte" Presto, 4/4 time, C major. Depicts the architect Arthur Troyte Griffith frantically practicing the piano, despite struggling.

Variation 8 "W.N" Allegretto, 7/8 time, G major. Taken from the initials of Winifred Norbury, a friend who lived in an 18th-century style mansion. The musical character is elegant and approachable, reflecting her deep love for music. The final note of this variation is extended into the next, Variation 9.

Variation 9 "Nimrod" Adagio, 3/4 time, E-flat major. This is the most famous variation in the set, often performed independently as an encore piece. The title "Nimrod" is the nickname of August Jaeger, Elgar's close friend and understanding confidant. The name Jaeger means "hunter" in German, and it is said to have been named after Nimrod, the mighty hunter in the Old Testament. Jaeger was a music magazine editor and an irreplaceable presence for Elgar, encouraging and motivating him when he fell into a slump. Jaeger is said to have rescued Elgar from the depths of his slump by citing Beethoven, another great composer who also battled repeated slumps. This piece, as a memento of their friendship, is infused with elements of the theme from the second movement of Beethoven's "Moonlight" Sonata.

Variation 10 "Dorabella" Allegretto intermezzo, 3/4 time, G major. "Dorabella" is a character from Mozart's opera "Così fan tutte," and the nickname of Dora Penny. Her speaking and laughing voices are expressed through the music.

Variation 11 "G.R.S" Allegro di molto, 2/2 time, G minor. "G.R.S" are the initials of George Robertson Sinclair, organist of Hereford Cathedral. This piece depicts his dog Dan playfully jumping into the river.

Variation 12 "B.G.N" Andante, 4/4 time, G minor. A piece named after Basil G. Nevinson, a cellist who formed a trio with Elgar and H.D.S-P from Variation 2. It is said that Elgar's later masterpiece, the "Cello Concerto," would likely not have existed without Nevinson's presence.

Variation 13 "***" Romanza: Moderato, 3/4 time, G minor. Indicated by symbols rather than letters, this is the only piece whose mystery of who it depicts remains unsolved. The quotation of the theme from Mendelssohn's Overture "Calm Sea and Prosperous Voyage" is key to solving the mystery of this piece. Theories, such as it depicting the noblewoman Mary Lygon or Elgar's former fiancée Helen Weaver, are still debated among scholars.

Variation 14 "E.D.U" Finale: Allegro – Presto, 4/4 time, G major. "E.D.U" stands for Edu, which is Elgar himself. It comes from his wife Alice affectionately calling him "Edu." This self-portrait-like piece is depicted in a heroic march style, but it reminiscently interweaves Variation 1 and Variation 9. Variation 1 and Variation 9 represent his beloved wife Alice and his understanding confidant Jaeger, respectively. It is a truly clever touch characteristic of Elgar to bring these two irreplaceable and important figures back into the finale.

So far, we have deciphered the first of the two mysteries Elgar embedded in the "Enigma Variations" – the one hidden in the initials of the piece's titles. However, the second mystery remains.

Elgar described this mystery as "an unplayed hidden theme that runs through the entire work." Regarding this "hidden theme," many hypotheses have been put forward by musicologists, ranging from representative British songs like the British national anthem, "Auld Lang Syne," and "Rule, Britannia!" to classical masterpieces by Mozart and Brahms, but none have been definitively solved.

Even in the 21st century, the mystery of this piece remains unsolved, but perhaps this mysterious charm is precisely why the "Enigma Variations" continues to captivate people's hearts.

As one of Elgar's representative works, and as an orchestral variation piece, it is often compared to Rachmaninoff's "Rhapsody on a Theme of Paganini" and Brahms's "Variations on a Theme by Haydn," and continues to be loved by many people around the world.