It’s 2019, and Alanis Morissette has traded her flicked cigarettes for peace signs.

Straddling a chair in the middle of the Apollo Theater on Monday night, the singer radiates tranquility, apparently unbothered by what she looks like when she hits the high notes. And, yes, 25 years since the release of her seminal and generation-defining album “Jagged Little Pill,” Morissette does in fact still hit them, quipping that singers that look “pretty” while doing it are lip-synching.

Without context, Morissette’s special one-night-only acoustic show at the Apollo could be a continuation of her 1999 MTV “Unplugged” set. But it doesn’t take long to realize that this version of Morissette is not the same person. The singer, now 45, has been married for 10 years and has three kids — one of which she gave birth to over the summer. Unlike some of the darker subject matters in her lyrics, Morissette charms the audience with her playfulness, teasing herself about her Canadian heritage and how she can’t hear anything in the crowd. She’s clearly no longer the angsty young woman who penned “Jagged Little Pill,” although to judge by the hearty sing-a-longs taking place at the venue on Monday night, the crowd had been craving a dose of nostalgia.

It makes sense: “Jagged Little Pill” has been getting the throwback treatment on-screen — first in the film “Lady Bird,” when Lady Bird (Saoirse Ronan) listens to “Hand In My Pocket” in the car and tells her dad that Morissette wrote the song in one hour, and then in a show-stopping karaoke performance of “You Oughta Know” in the Olivia Wilde-directed “Booksmart.” Both banner musical moments have brought Morissette’s music to a new generation while allowing past fans a chance to revisit and rediscover them. There will also continue to be no shortage of it, considering Morissette’s era-defining album inspired a Broadway musical of the same name opening Thursday, and a tour around the album’s 25th anniversary next year.

While the deeply personal “Jagged Little Pill” was one of the biggest-selling albums — it’s been certified a whopping 16-times platinum by the RIAA — in the music industry’s most lucrative era — the ‘90s — it was also misunderstood. Morissette’s fury toward industry sexism and her own personal trauma often were discounted, her lyrics criticized as trite, and she — like Liz Phair and other young female artists coming of age at the time — wasn’t taken as seriously as she might have been. Plus, as Letters to Cleo singer Kay Hanley has said, when Morissette was coming up in the ‘90s, there was really only one slot available for songs by women in rock radio. But nearly two-and-a-half decades later, the album is getting a thorough and much-deserved second chance in the spotlight.

The show, which is largely a trip down memory lane, saw Morissette authoritatively embracing her past. But the trauma and pain that one seeped through the album is replaced with peace — empathy for her younger self and a confidence in her present. She also brought her music even further into the present with lyrical twists: trading “CDs” for “mp3s” on “Your House” and meeting the man of her dreams and his “beautiful husband” instead of a “wife” on “Ironic.”

At the same time, no matter how harsh the melodies of the original “Jagged Little Pill” tracks, Morissette re-shaped the sounds to soothe on acoustic guitar. With the hits “Hand in My Pocket” and “Head Over Feet,” the singer turned pop jaunts into lullabies, with her signature yodel intermittently cutting through; plus, she proved she can still play a mean harmonica. When she reached one of her biggest hits, “Ironic,” Morissette embraced the sing-a-long, letting the audience take over half the track for her. The singer also thrived in the quieter moments of the show when she performed “Perfect” and “Wake Up,” honing in on her haunting, stripped-back tone.

But diverging from the overall calmer tone of the evening, Morissette’s “Right Through You,” which detailed her experiences with industry sexism and harassment long before #MeToo, remained as biting as ever.

In-between “Jagged Little Pill” tracks, Morissette dropped in two new songs she penned for the musical: the moody “Smiling,” which could have been an outtake from the original album, and the harrowing “Predator,” a song about sexual assault. Straying from a typical encore, Morissette remained onstage before closing out her set with two non-“Jagged Little Pill” hits; she delivered a jaw-dropping crescendo during her power ballad “Uninvited” before aptly closing the show with her gratitude anthem “Thank U.”

In her acoustic set, Morissette found a new kind of liberation within the songs of “Jagged Little Pill,” allowing her to rewrite its narrative on her own terms, with 25 years of hindsight.