Leonardo Antonio Pellegrino, who performs as Leo P, was born in Pittsburgh on June 3, 1991, the youngest son of the accordionist and composer Stephen Pellegrino. He began on clarinet, playing polkas with his father, and says hearing John Coltrane pushed him toward the saxophone. He took up the baritone in a school ensemble when the regular baritone player became unavailable, and it stuck. He moved to New York in 2010 on a scholarship to the Manhattan School of Music and graduated in 2013. While still a student he recorded with the school's Afro-Cuban Jazz Orchestra on ¡Qué Viva Harlem! (Jazzheads, 2014), conducted by Bobby Sanabria, and Scott Yanow's review of it in Down Beat singled out the extreme high notes in his solo on "Let There Be Swing."

At school he met the trumpeter Matt Muirhead. With the drummer David Parks, whom he knew from busking, he began playing in New York subway stations in mid-2013 under the name Too Many Zooz, a style the trio calls brass house and defines as a mix of jazz, Afro-Cuban rhythms, funk, EDM and house music. A video shot at the Union Square station went viral in March 2014, and the group issued its first EP, F NOTE, that January, selling it from the platform. Pellegrino was also a member of the brass band Lucky Chops, whose 2016 subway video of "Funky Town" and "I Got You (I Feel Good)" featured him; Wikipedia dates his time in that band from 2014 to 2017, and he is credited on its 2016 album NYC.

Too Many Zooz's first full-length album, Subway Gawdz, came out on June 27, 2016. That July they appeared on Kaskade's single "Jorts FTW," and on November 2, 2016 they backed Beyoncé and the Dixie Chicks (now The Chicks) on "Daddy Lessons" at the 50th Country Music Association Awards in Nashville. Their song "Warriors" turned up in a Google Pixel 2 advertisement in October 2017 and in the flag parade of the 2018 Eurovision Song Contest final, and "Brnx Bmbr" in a KFC commercial. The band's later records include the EPs A Very Too Many Zooz Xmas (2018), ZombiEP (2019) and Red Apple Gift Shop (2025) and a second album, Retail Therapy (March 8, 2024).

The clearest jazz-side evidence comes from outside the trio. On August 25, 2017 he appeared as a guest of the Metropole Orkest at the BBC Proms in a program of Charles Mingus's music, where the Guardian's John Fordham noted his hook-punctuated baritone playing and his dance moves, and that November he played Ronnie Scott's in London with Too Many Zooz. He is a guest on the alto saxophonist Grace Kelly's Go Time: Brooklyn 2 (2018), where he is credited on baritone saxophone and as the writer of "Fish & Chips," and on November 30, 2019 the two announced 2SAXY, an alto and baritone duo. In 2019 he also began Thundersmack with Michael Wilbur of Moon Hooch, whose 2020 single "STONK" features him. He joined the saxophone section of The 8-Bit Big Band for Backwards Compatible (2021), and a Jazz Journal review picked out his centre-stage feature on "Super Mario Land Underground," over a two-chord vamp, for its multiphonics and altissimo control. The same album contains "Meta Knight's Revenge," the arrangement that won the 2022 Grammy for Best Arrangement, Instrumental or A Cappella; Pellegrino's feature is on a different track.

His first full solo album, Comin' Up Aces, billed by Shanachie as his debut, was released by that label on November 4, 2022 and produced by his friend Tom Wilson. Ten tracks, seven of them originals, run through funk, blues, salsa and New Orleans grooves, with Mingus's "Goodbye Pork Pie Hat," Eddie Harris's "Cold Duck Time" and Earth, Wind & Fire's "Serpentine Fire" as the covers. Richard Elliot plays tenor saxophone and the trumpeter Eric "Benny" Bloom of Lettuce plays on "Cold Duck Time," and the Galactic drummer Stanton Moore plays on "Issa Blues." It followed Sax Star Suite Pt. 1, a six-track set he put out independently in April 2018. In 2022 he also contributed to the soundtrack of Damien Chazelle's film Babylon, and in 2026 he is a featured artist on "Whisky Peak Saloon," an insert song for the second season of Netflix's live-action One Piece.

In the summer of 2025 he toured as the baritone saxophonist of Dave Koz and Friends' Summer Horns, a run that opened July 17 in Red Bank, New Jersey, and ended at the Hollywood Bowl on August 31, alongside Marcus Anderson on saxophone, Jeff Bradshaw on trombone, Evan Taylor on trumpet and Marcel Anderson on vocals. He is a member of Too Many Zooz and was announced as a Yamaha artist in March 2019, playing a Yamaha YBS-52 baritone.

Pellegrino is two things at once, and the profile says so plainly. In Too Many Zooz he plays dance music: brass house is built on house and EDM grooves, the baritone takes the part a synthesizer bass line would take in a club track, and the act is as much about his dancing and costume as the notes. Outside the trio he is a working jazz and jazz-funk soloist, trained at a conservatory, recorded with a Latin jazz orchestra, invited to the BBC Proms for Charles Mingus's music, and the leader of a Shanachie album that its label describes as jazz-funk meant to make jazz danceable again. Retailers and reviewers variously file that record under jazz-funk and smooth jazz.

He names the baritonist Ronnie Cuber as his favorite player on the instrument, and lists Michael Brecker, David Sanborn, Gerald Albright, Eric Dolphy, Miles Davis and Duke Ellington among his inspirations, along with Prince, Michael Jackson, George Clinton and Tower of Power. On Comin' Up Aces he credits Eddie Harris for showing him that a tune does not need many chord changes, and Maceo Parker as the inspiration for the title track. His label's biography and a Jazz Journal reviewer both single out his range, with notes above the baritone's normal compass, and the control he shows there.