I doubt Hannu Lintu’s Sibelius would sound the way it does here had the conductor not been so deeply involved in the exploratory projects that make up the bulk of this set’s 10-hour playing time. In the introductory documentary we see the conductor working through the known knowns of Sibelius’s various mental and creative states in Vienna, Berlin, Rapallo, Stockholm, Helsinki and other cities associated with the symphonies. Before each performance with the Finnish Radio Symphony Orchestra, filmed live at the Helsinki Music Centre, Lintu and the composer Osmo Tapio Räihälä engage in movement-by-movement analyses of each symphony’s themes (relevant notation appears under footage of the orchestra demonstrating said themes in the Centre’s basement studio). Lintu has always had an interesting analytical perspective on the symphonies but he delves even further here. One strand he appears to enunciate in both his commentary and his performances is that Sibelius was wild and untempered at the time of the First Symphony; that the tragedy of infant death led to the searching, tortured elements we hear in the Second; and that he relaxed into his unique concept of symphonic construction with the Third.

Still, I find it hard to reconcile Lintu’s histrionic, borderline caricature approach to the First Symphony. But it tells us what’s in store aesthetically: delicious orchestral blend; intensely disciplined strings (though Lintu doesn’t articulate with the forensic detail of Osmo Vänskä); some outstanding individual players; understated camerawork; and a photogenic hall whose dark seating and off-white stage were built for TV broadcast. Enshrined in that is something else, too: an important and unparalleled audiovisual document of a Finnish orchestra, audience and venue close-up in a landmark year for the country. What you see feels entirely of the here and now; the series of elegant butterfly tattoos that runs up the right forearm of harpist Laura Hynninen is so redolent of time and place while somehow sensitive to this winged music as well.

In the Second Symphony, Lintu is less hot-headed, underscoring the score’s introspective working-out and shades of tragedy. The Andante is painfully tender but the striving hymn of the finale is played relatively straight before an unusually defiant last page. Lintu has fascinating ideas about the Third Symphony and its thematic origins in Sibelius’s abandoned cantata Marjatta. There’s a neat, circumspect build-up to the opening Allegro’s blossoming into its ‘sleigh-ride’ theme and a Parsifal-like luminosity to the way the movement’s final chord rests. The feeling in Symphony No 4 is that the music isn’t so much being wrenched from the soil as glimpsed somewhere on the horizon, intangible. The Largo is intensely confessional and the final Allegro feels like a bid for escape, its strain foreshadowing the music to come.

Lintu’s unusual choreographing of the contrary-motion outfolding in the Fifth’s opening movement jarred initially but perhaps works in the context of what comes after. There is something riveting and unshakeably secure about this performance, the strings and brass of the Finnish RSO magnificent at that first movement’s final, excitable ascent. As in the Third’s Andantino, the Fifth’s Andante is filled with air, Lintu standing back slightly to let the rhythmic patterns find their own equilibrium. He introduces a touch more expanse at the modulation of the Swan theme in the finale, which makes for an palpable sense of flight; the twisting melee that prefaces the farewell jabs has a good combination of resistance and momentum.

In keeping with that idea of a linear cycle, the Sixth isn’t exactly light but is well sprung, Lintu’s sensitive spotlighting of themes a consistent feature. In the Seventh Symphony it’s a case of balancing some pluses with some minuses: Lintu can’t quite unite the varying tempi under a meta-flow like Paavo Berglund could, which makes for a slightly episodic feel, but once again his sense of strain is revealing, as in the bars before the first trombone solo. Lintu, his face always a picture, can really spur his orchestra on to find another gear when it needs to.

To describe this as an important snapshot of orchestral Helsinki in 2015 is to belittle the touching gift that is Finns offering us their greatest music with such undemonstrative heart and soul. In the same vein, perhaps the icing on an undeniably epic cake of performance and analysis is Piia Hirvensalo’s kooky documentary series Sort of Sibelius. Here we get psychology, psychiatry, philosophy, graphology, toxicology and even mixology: a delightful sequence in which two professional alcohol pundits attempt to drink like Sibelius did. In a word, unparalleled.