With the release of his new three-disc set of Mendelssohn’s complete symphonies on Deutsche Grammophon, Yannick Nézet-Séguin seems caught somewhere between a shotgun wedding and an artistic breakthrough.

The set builds on the success of Nézet-Séguin‘s 2014 Schumann symphony set with the Chamber Orchestra of Europe that reimagined this core symphonic repertoire with smaller-scale forces the composer would’ve known in his own time. So moving on to Schumann’s contemporary Mendelssohn, also with the Chamber Orchestra of Europe, makes good recording company sense — especially amid the vogue for recording symphonic cycles in one fell swoop (note recent Brahms symphony cycles from Boston and Berlin).

But that logic starts crumbling when you take a close look at the Mendelssohn’s five symphonic specimens: Not only are they a motley quintet, but could anything be more unsuited to Nézet-Séguin‘s temperament?

Anyone who has even casually admired the Philadelphia Orchestra music director's concerts knows how much he is attracted to composers' late-period works, the ninth symphonies that contemplate the mysteries of the hereafter. Mendelssohn (1809-47) didn't have a late period, and, according to some accounts, had given up composing when he died. His best-known works feel so polished, so perfected they leave little room for interpretation.

Mendelssohn was perhaps the ultimate Biedermeier composer, most inspired with his miniature Songs Without Words or when portraying the fairies and rustics of Shakespeare’s A Midsummer Night’s Dream. Elsewhere, he mainly reveals himself in the Violin Concerto. But he generally has none of the operatic temperament that Nézet-Séguin seizes upon in other composers to create such compelling performances. That’s where the project begins resembling a shotgun wedding.

When I first heard the radio broadcasts that preceded these recordings, I offered condolences to Nézet-Séguin for getting stuck with the almost-never-heard Symphony No. 1 — an obligatory part of the complete Mendelssohn symphonic cycle.

"You don't like it? Even when I conduct it?" he asked with ironic hubris.

Well, he always has been one to stand behind everything he conducts. Yes, even a work like this, whose first movement seems like so much synthetic angst. But, sure enough, in the edited and polished final product on Deutsche Grammophon, the Symphony No. 1 starts sounding viable.

The second movement hasn't much memorable melodic content but does have some gracefully rendered wind solos — the hallmark of a Chamber Orchestra of Europe performance. The third movement is what draws me back to the symphony repeatedly, with an off-kilter waltz rhythm in which the mask of social respectability keeps falling off. The bustling final movement is still much ado about little. But the great third movement wouldn't mean as much without the other movements around it.

Nézet-Séguin concentrates his best efforts where he can do the most good, and that would be the Symphony No. 2 (“Hymn of Praise”), which isn’t even a symphony and apparently wasn’t regarded as such by the composer, though his posthumous publisher thought otherwise. It’s an oratorio of sorts — a series of psalms musicalized for chorus and vocal soloists. This is the triumph of the set, and it’s Nézet-Séguin‘s artistic breakthrough.

Often heard with a large, wall-of-sound Victorian-style choir, Symphony No. 2 benefits from the smaller-scale performance here, which reveals more content, and more compelling content, to the extent that this performance may be a new landmark in the piece's scant recorded history.

Some of Mendelssohn's religious works leave a funny taste, considering that he was raised in a Jewish household but was baptized Lutheran (on Bach's birthday, no less). But this performance reveals a sincerity that makes you think that piece was written from a deeply genuine place.

Mendelssohn's ever-popular Symphony No. 3 ( "Scottish") and Symphony No. 4 ("Italian") might be called tourist symphonies — works based on local color the composer soaked up on his travels, and portrayed from a safe, picturesque distance. Engaging, tuneful, and meticulously well-wrought, these symphonies often thrive on the kind of atmosphere enabled by larger symphony orchestras, which is not part of the deal on this new set.

The challenge is to make interpretive points with less sound, and in the Scottish symphony that definitely happens, with a lot of subsidiary motifs often not heard at all in larger-orchestra performances. The final movement shows Nézet-Séguin at his smartest, giving repeated rhythms a nagging anxiety and accompanying figures a wiry intensity, with a keen instinct for where to turn up the heat.

The Symphony No. 4 is the least notable performance on the set. Nézet-Séguin sets off a sympathetic framework that keeps the music appropriately buoyant, and just lets the music carry itself.

Symphony No. 5 ("Reformation") incorporates hymns such as Martin Luther's A Mighty Fortress Is Our God and is easily the most substantial of the five, even though its severity hasn't won an audience to the extent of the sunnier Italian symphony. Often in these works, Mendelssohn embraces Bach-like fugal writing, always with great technical success but sounding more like an assignment than a heartfelt expression.

Yet with lots of different elements kept in play during this symphony, Nézet-Séguin seems thoroughly engaged, finding meaning in the way the pieces play off of one another.

This last work benefits from the conductor’s trademark cumulative energy that builds throughout any given movement. The orchestral playing is occasionally smudgy, and one feels the lack of larger-orchestra heft. Whether or not Mendelssohn intended so much sound to be thrown at his symphony, the music certainly benefits from it. So even if the classic RCA Boston Symphony Orchestra recording under Charles Munch is a better choice, you appreciate it anew after hearing the insights of Nézet-Séguin.

The set as a whole is a solid traversal of the five symphonies, with as much of a consistent approach as one could hope for in such different works.