It has become a cliché with a certain kind of critic to say that Mendelssohn never fulfilled the promise of his youth. Such a charge is a pretty tough thing to say about someone who died at 38 – most of us would think Mendelssohn never made it out of his youth. And such a charge overlooks the great works Mendelssohn completed in the years just before his death: the Violin Concerto, the complete incidental music for A Midsummer Night’s Dream, and Elijah. But there can be no gainsaying the fact that the young Mendelssohn was a composer whose gifts and promise rivaled – perhaps even surpassed – the young Mozart’s. The child of an educated family that fully supported his talent, Mendelssohn had by age 9 written works that were performed by professional groups in Berlin. At 12 he became close friends with the 72-year-old Goethe, at 17 he composed the magnificent Overture to A Midsummer Night’s Dream, and at 20 he led the performance of the St. Matthew Passion that was probably the key event in the revival of interest in Bach’s music.

Mendelssohn completed his Octet in October 1825, when he was 16. One of the finest of his early works, the Octet is remarkable for its polished technique, its sweep, and its sheer exhilaration. Mendelssohn’s decision to write for a string octet is an interesting one, for such an ensemble approaches chamber-orchestra size, and a composer must steer a careful course between orchestral sonority and true chamber music. Mendelssohn handles this problem easily. At times this music can sound orchestral, as he sets different groups of instruments against each other, but the Octet remains true chamber music – each of the eight voices is distinct and important, and even at its most dazzling and extroverted the Octet preserves the equal participation of independent voices so crucial to chamber music.

Mendelssohn marked the first movement Allegro moderato, ma con fuoco, and certainly there is fire in the very beginning, where the first violin rises and falls back through a range of three octaves. Longest by far of the movements, the first is marked by energy, sweep, and an easy exchange among all eight voices before rising to a grand climax derived from the opening theme. By contrast, the Andante is based on the simple melody announced by the lower strings and quickly taken up by the four violins; this gentle melodic line becomes more animated as it develops, with accompanying voices that grow particularly restless.

The Scherzo is the most famous part of the Octet. Mendelssohn said that it was inspired by the closing lines of the Walpurgisnacht section near the end of Part I of Goethe’s Faust, where Faust and Mephistopheles descend into the underworld; he apparently had in mind the final lines of the description of the marriage of Oberon and Titania:

Clouds go by and mists recede,

Bathed in the dawn and blended;

Sighs the wind in leaf and reed,

And all our tale is ended.

This music zips along brilliantly. Mendelssohn marked it Allegro leggierissimo – “as light as possible” – and it does seem like goblin music, sparkling, trilling, and swirling right up to the end, where it vanishes into thin air.

Featuring an eight-part fugato, the energetic Presto demonstrates the young composer’s contrapuntal skill. There are many wonderful touches here: at one point sharp-eared listeners may detect a quotation, perhaps unconscious, of “And He Shall Reign” from the “Hallelujah” Chorus of Handel’s Messiah, and near the end Mendelssohn skillfully brings back the main theme of the Scherzo as a countermelody to the finale’s polyphonic complexity. It is a masterstroke in a piece of music that would be a brilliant achievement by a composer of any age.

Eric Bromberger is a regular contributor to the Los Angeles Philharmonic program book.