“A single death is a tragedy, a million deaths a statistic.” At the start of the Boston Symphony Orchestra’s all-Shostakovich concert at Carnegie Hall on Thursday, the cellist Yo-Yo Ma invoked this darkly cynical statement attributed to Stalin. Addressing the capacity crowd, which included Shostakovich’s son Maxim, Ma added: “We play Shostakovich so that no death is ever just a statistic.”

Historians disagree on how Shostakovich, the Soviet Union’s most famous composer, felt about the political system that alternately boosted and threatened his career. But the juxtaposition of the individual and the collective, of a singular human experience set against the mass movements of history, drives much of the drama in his symphonic music.

During the orchestra’s two-night visit to New York, the Boston players, led by their music director Andris Nelsons, gave bravura performances of Shostakovich — his 11th and 15th symphonies, as well as the Cello Concerto No. 1 — that reveled in the sonic riches of this contradiction-laden music. But there was also an emotional reserve, even primness, to much of the playing that exacerbated the music’s ambivalence and left a listener with more questions than answers.

That is disappointing, given that Nelsons has made Shostakovich a central mission of his tenure in Boston. Last month, he and the orchestra capped a 10-year recording marathon of all the composer’s major works with the issue of a 19-disc box set, including Grammy-winning recordings.

The quality of the music-making at Carnegie Hall was never in doubt. The Boston brass section was a marvel of cohesion, whether in the reverent chorale that opened the second movement of 15th Symphony on Wednesday or in the harrowing violence of the second movement of the 11th, performed on Thursday, which depicts the brutal repression of a peaceful protest in St. Petersburg in 1905.

There were radiant solos on Wednesday by the principal cellist Blaise Déjardin and tartly virtuosic ones by the concertmaster, Nathan Cole. Shostakovich’s sarcastic humor was finely rendered in the first movement of the 15th with its cartoonish quotations of Rossini’s “William Tell” overture and in the militant jauntiness of the cello concerto’s first movement, in which the orchestra heckles the frenetic, hyperactive soloist.

But the orchestra never matched Ma’s passionate commitment. At moments in the concerto, the orchestra smothered his hard-driving fast passages. Or a gesture Ma played with agonized urgency would be picked up and developed by the orchestra with brilliant sound but bland expression. Coordination between Ma and the ensemble was sometimes off by a hair.

There were similar issues in the interplay with the soloist in the first half of Wednesday’s program in a fragmented reading of Beethoven’s Piano Concerto No. 4, with Mitsuko Uchida as the soloist. Next to her characteristically sensitive playing, the orchestra moved with a heavy tread that made for some inattentive entrances and a general feeling that pianist and orchestra were playing in different rooms.

Reflecting on the theme of individual and collective power that Ma brought out on Thursday, I couldn’t help wondering about the difference between the fluid expressivity of individual solos in the orchestra and the contained playing of the group. To be sure, Shostakovich’s music requires a conductor to patiently marshal forces so that a sonic outburst like the massacre scene of the 11th Symphony rings out with traumatic force. Nelsons does this well but could do more to convey some of the trust and freedom of his musicians’ solos in ensemble passages, too.

Still, the discipline paid off at the end of the 15th on Wednesday. At the finale of the enigmatic last movement, with its dreamlike echoes of Wagner, the sound tapers to a pale thread of strings. The violins start up a hushed, unexpectedly tender dance that is eventually interrupted by slashing chords and the insistent tapping of a snare drum. The final minutes unfold over an eerie thin drone with only the sound of the percussion section whirring and ticking like a cosmic clock running on in a world devoid of humans.

In that moment beyond history and individual consciousness, Nelsons drew beautifully impersonal playing from the orchestra that highlighted the bewitching mystery of the music.