Sibelius completed this work in February 1923, and conducted the premiere at Helsinki on February 19 of that same year. His first reference to the work, in 1918, described it as "wild and passionate in character. Dark with pastoral contrasts. Probably in 4 movements...intensifying in a dark orchestral swell [until] the main theme is drowned." At the same time he cautioned that his plan could change -- and how it did! -- "depending on the way my musical thinking develops. I am always a slave to my themes and obey their demands." Some of that "wild character" found a home in the last version of Symphony No. 5 (1919). The Sixth, however, evolved as a virtual homage to Palestrina, the same Renaissance master honored in Hans Pfitzner's then young opera, Palestrina.
In common with the Seventh Symphony, his incidental music for Shakespeare's The Tempest, and the tone poem Tapiola (Sibelius' last orchestral works before he quit composing altogether in 1929), the Symphony No. 6 is nature-painting uncluttered by "civilized" detritus. Even the fauna indigenous to subarctic Finland are absent, leaving only some bird-like motifs. It is the purest, most inward, in many ways most fascinating of his symphonies. For some of us it is also the most hypnotic, to be heard countless times without ever revealing all of its secrets.
The first movement, Allegro molto moderato, nominally in D minor, more accurately can be said to inhabit the medieval D Dorian mode (that is to say, from D to D on the white keys of the piano, whereas "natural" D minor has a flatted B, and "harmonic" D minor has a sharped C). This lends the music an archaic character that nevertheless becomes passionate as it evolves, praising the presence of God and ghosts in a cathedral of sound. Sibelius shifts into C major, however, and mostly stays there until a radiantly calm coda in D Dorian, as if there had never been C major! Nicolas Slonimsky wrote of "thematic molecules" (Cecil Gray called them "cells"), played in thirds by pairs of instruments. While these may seem random on first hearing, their development integrates everything as if by alchemy.
The second movement, Allegretto moderato serves, as in Beethoven's Eighth, in place of a slow movement, although Sibelius at one time thought of retitling it Andantino (lest conductors play it too briskly, as Georg Schnéevoigt did in the first recording in 1934). After a soft bid for attention on a drum tuned to F, flutes and bassoons play free-floating chords that resolve in G Dorian. Subtly, a 3/4 rhythmic pattern takes over as notes-per-measure increase from three to six to nine to 12. Scalar passages ascend only to fall partway back, while a saucy motif repeats itself until the ear is haunted for days after. The Poco vivace third movement is a brief scherzo in jig time (thus spoke Slonimsky). But it has no trio, no B section; thematic molecules from earlier movements are adapted, reorganized, and become boisterous right up to the end.
In the Allegro molto finale, Sibelius completes the C major first half of the opening motif in D Dorian. This is the symphony's densest movement texturally, the closest it comes to the 1918 promise of passion (but it is never wild). Indeed, Sibelius here echoes the nature poems he wrote from the Fourth Symphony on -- as well as Tapiola to come. In structure this comes closest to a conventional sonata-rondo, yet it is never traditional or predictable. The word concludes with quiet, undecorated D Dorian chords.