Starring Tony Award nominee Ernestine Jackson, “Lady Day at Emerson’s Bar and Grill” captures one of Lady Day’s — Billie Holliday’s — last performances, four months before her death in 1959.

In a show about someone known by her voice, Jackson’s singing becomes paramount. Her vocal tone evokes Billie Holliday, applying “a blues feeling to a jazz beat” as Holliday says. At times, however, the artificial sound she creates in order to imitate Holliday slips. Jackson also has a beautifully broad tone but one which does not quite compare to the directness of Holliday’s sound. Vocal tone aside, Jackson interprets Holliday’s music with gestures that would make the Lady Day proud.

What drives the show is not a simple revue of Holliday’s music, but instead a portrait of the artist in both the glory and misery of her last days. In this Jackson does an admirable job of capturing the 44-year-old jazz royal. But the Billie Holliday that Jackson creates seems far older than her age would suggest. This Holliday moves like a feeble and haggard woman in her late ’60s or ’70s, completely lacking fluidity in her movement.

But Jackson still does a good job portraying the artist who created classics like “God Bless the Child” and “Strangefruit.” The deeply personal nature of Holliday’s music comes through in the show, as the themes and events that inspire her music come out in her commentary. The strongest, and most subtle of her songs is “Strangefruit,” a Holliday hit song describing the endemic racial injustice of her time. The importance of race comes through in the show in that nearly all of her anecdotes are framed in the context of being black. Its lyrics bring out this dimension, but just as importantly, they also show Holliday as a tired star: tired of making the same music over and over because audiences clamor for the same song night after night.

Supporting Jackson and providing her accompaniment is a jazz combo with bass, drums and piano. Holliday’s pianist Jimmy Powers (Darryl Ivey) plays a particularly critical role in this endeavor. As the only other listed cast member of the production Powers speaks only a few times, but makes his most important communication without words. By edging Holliday on through striking a chord or playing the first notes of a melody, he provides the foil that exposes Holliday’s unfocused confusion.

The pacing of the Lady Day leaves something to be desired. While it only runs 90 minutes long (without an intermission), it isn’t until more than halfway through that the audience feels drawn into the life of the character. Billie finally clicks as she begins to meltdown. When this moment occurs, you can’t avert your eyes from the internal drama and conflict on the stage.

James Noone, set designer for the production, succeeds in creating an environment where those in the hall feel almost as if they were sitting in Emerson’s Bar and Grill in 1959, waiting for Billie Holliday to come out for her set. Here a principal advantage is the Long Wharf theatre itself, where the audience is seated in front and on two sides of the stage. Thrusting the scene almost out into the audience works well for this piece, as it replicates the intimacy of a small jazz club. This enables audience members to imagine they are watching Billie Holliday right in front of you on stage.

On the whole, the lighting design contributes to the feeling of a night club. The haze filtered through the scattered lights of the set captures the smoky, dim quality. However, the lighting changes between song and speech are often too pronounced. Although it is important to signify the difference between Holliday speaking and Holliday singing, this changes create too much of a dichotomy between the two states rather than recognizing that in both Holliday is the primary focus.

Lady Day provides an opportunity to glance into the life of a jazz legend, replete with complications but also with reminders of what made Billie Holiday legendary — well worth an evening trip to the Longwharf Theater.