Gary Smulyan was born on April 4, 1956 in Bethpage, on Long Island, and started on alto saxophone as a teenager. Long Island in the early 1970s still had a working jazz scene within reach of a schoolboy with a horn, and while he was still in high school he got onto bandstands with Chet Baker, Lee Konitz, the trombonist Jimmy Knepper and the violinist and cornetist Ray Nance. He went on to SUNY Potsdam and then Hofstra University, and at twenty-two, in 1978, he left school for the road: Woody Herman hired him for the Young Thundering Herd, by then on baritone rather than alto. The band he joined was unusually loaded with players who would matter later, among them the tenor saxophonist Joe Lovano, the bassist Marc Johnson and the drummer John Riley, with Frank Tiberi as Herman's musical deputy. A November 1978 concert in Chemnitz, then in East Germany, has been issued three separate times and is the clearest surviving document of that edition of the band.

Two years of Herman's bus ended in 1980, and Smulyan moved into New York rather than out of it. He took the baritone chair in the Mel Lewis Jazz Orchestra, the Monday-night band at the Village Vanguard that Mel Lewis had co-founded with Thad Jones in 1966 and was by then running under Bob Brookmeyer's musical direction. He has held that chair ever since. The first record of it is Make Me Smile & Other New Works By Bob Brookmeyer, taped at the Vanguard over five nights in January 1982, where the credits list him fifth in the saxophone section on baritone and bass clarinet and put Earl Gardner on first trumpet. Lewis died in February 1990 and the band continued as a cooperative under a new name, the Vanguard Jazz Orchestra, with Smulyan still on baritone; he is on its records from Lickety Split in 1997 through Overtime: Music Of Bob Brookmeyer in 2014, and on the Monday-night stand between them. Around that anchor he accumulated more section work than almost any baritone player of his generation: the Mingus Big Band, the Smithsonian Jazz Masterworks Orchestra, Jon Faddis's Carnegie Hall Jazz Band, the Dizzy Gillespie All-Star Big Band under Slide Hampton, the Gene Harris Philip Morris Superband, Carla Bley's big band, the posthumous Gil Evans Orchestra, Gerald Wilson's orchestra, and Dave Holland's big band and octet, which he anchored for the best part of a decade.

He waited a long time to record under his own name. The Lure Of Beauty came out on the Dutch label Criss Cross Jazz in 1991, when he was thirty-five: a quintet with Jimmy Knepper's trombone, Mulgrew Miller, Ray Drummond and Kenny Washington, five of whose nine tunes he wrote. Criss Cross kept him for four more albums across the 1990s, and each one is built on a different idea rather than a repeat of the last. Homage, cut on December 18, 1991 and released in 1993, is eight compositions by Pepper Adams and nothing else, recorded eighteen months after Adams's death with Adams's own pianist Tommy Flanagan at the keyboard, and annotated by Gary Carner, the man who would later write Adams's biography. Saxophone Mosaic (1994) puts him in front of a six-saxophone front line arranged and conducted by Bob Belden, with Dick Oatts, Billy Drewes, Ralph Lalama, Rich Perry and Scott Robinson filling out the reeds; WBGO named it one of the best twenty-five jazz records of its year. Gary Smulyan With Strings (1997) sets the baritone against nine strings on ballads and film themes, again in Belden's arrangements, with liner notes by Stanley Crouch, and the Boston Globe put it among the ten best jazz CDs of the year. Blue Suite (1999) drops the reeds entirely and pits him against a nine-piece brass choir of trumpets, trombones, French horns and tuba, with Bill Charlap, Christian McBride and Kenny Washington behind him and Earl Gardner in the trumpet section.

The sideman list of those same years is a fair map of mainstream New York jazz. He played on Freddie Hubbard's MMTC (1995), Joe Henderson's orchestral Big Band (1996), Conrad Herwig's The Latin Side Of John Coltrane (1996), Cedar Walton's Roots (1999), George Coleman's octet date Danger High Voltage (2000), and Joe Lovano's 52nd Street Themes (2000), which reunited him with his Herman bandmate in a nine-piece band. He was in Gunther Schuller's reconstruction of Charles Mingus's Epitaph in 1989, played bass clarinet on two Tom Harrell records, and turned up on the pop side of the ledger too, behind B.B. King at the Apollo in 1990, behind Diana Ross at the Ritz in 1992, and on one track of David Byrne's Grown Backwards in 2004. In 1997 he joined Ronnie Cuber and Nick Brignola in the Three Baritone Saxophone Band for Plays Mulligan, twelve pieces associated with Gerry Mulligan played by three baritones and a rhythm section.

One credit from that stretch is the reason many listeners outside the jazz audience have heard him at all. In December 2002 the John Scofield Band recorded Up All Night at Long View Farm Studios in West Brookfield, Massachusetts, and the following January four horn players went into The Hit Factory in New York to overdub a section John Scofield had arranged himself: Craig Handy on tenor, flute and bass clarinet, Jim Pugh on trombone, Earl Gardner on trumpet and Smulyan on baritone. They play on six of the album's eleven tracks, over a rhythm section of Scofield, Avi Bortnick on rhythm guitar and loops, Andy Hess on bass and Adam Deitch on drums. The pairing of Smulyan and Gardner was not a coincidence of casting: by 2003 the two had been sitting in the same brass-and-reeds sections for twenty years, in the Mel Lewis Orchestra and the Vanguard Jazz Orchestra, in the Carnegie Hall Jazz Band, the Mingus Big Band, Dave Holland's big band and Carla Bley's, and on Smulyan's own Blue Suite, where Gardner is one of the three trumpets.

From 2003 the leader records came steadily and moved through three labels. Reservoir issued five between 2003 and 2008, including the two chordless trio sets Hidden Treasures (2006), a piano-less date with Christian McBride and Billy Drummond that took four and a half stars in DownBeat, and More Treasures (2007), both built from neglected compositions by working musicians rather than standards. High Noon: The Jazz Soul Of Frankie Laine (2008) is a nine-piece band on the repertoire of the pop singer, arranged by Mark Masters. Capri Records followed with the organ quartet Smul's Paradise (2012), on which Mike LeDonne plays Hammond and Peter Bernstein guitar, and Bella Napoli (2013), eleven Neapolitan songs sung by the actor Dominic Chianese with a jazz band behind him, which Smulyan also produced. Since 2018 he has recorded mostly for the Danish label SteepleChase: two chordless trio albums of contrafacts with David Wong and Rodney Green, Tadd's All, Folks (2022), eleven of Tadd Dameron's rarely sung songs with the young vocalist Anais Reno, and Boss Baritones (2024), a second two-baritone quintet, this time with Frank Basile. He has also duetted with George Cables on eight Thad Jones compositions for a numbered vinyl edition, Two For Thad (2016), and co-led European quintets with the tenor player Ralph Moore and with the Austrian drummer Bernd Reiter, who also brings him into Dameronia's Legacy All-Stars, the touring octet Reiter leads on Dameron's music alongside Jim Rotondi and Dick Oatts.

He has won his instrument's category in the critics and readers polls repeatedly since the late 2000s. DownBeat's own account of its 70th Annual Critics Poll names him the baritone saxophone winner for 2022, and the specialist site JazzBariSax reported him as the winner of the 61st poll in 2013; his own record of the polls adds roughly twenty more wins across DownBeat, JazzTimes and the Jazz Journalists Association awards between 2009 and 2024. He teaches: he is a lecturer in jazz studies at SUNY Purchase, and since 2006 has been artistic director of the Berkshire Hills Music Academy in South Hadley, Massachusetts, a two-year post-secondary music school for young adults with developmental disabilities. In October 2022 he helped launch Low Blow Music, a grassroots organisation for the promotion of the baritone saxophone, at the Brooklyn club Ornithology.

Smulyan plays the baritone the way bebop tenor players play tenor, at full speed and without the instrument's usual concessions, and that is the whole point of him. His own account of his lineage names Cecil Payne, Leo Parker, Pepper Adams, Serge Chaloff and Nick Brignola, the handful of baritonists who took the horn into fast chromatic music instead of using it as a section anchor or a ballad voice, and Adams above all: the hard, dry, driving sound and the willingness to attack a line rather than roll through it come straight from him, which is why Homage is an album of nothing but Adams tunes and why Adams's "Cindy's Tune" has turned up twice more in his book since. Harry Carney is the other name he gives, for tone rather than phrasing. What separates him from a pure Adams disciple is the range of settings he has been willing to write himself into as a leader: strings, brass choir, six-saxophone front line, Hammond organ, Neapolitan song, two-baritone quintet, and above all the chordless trio, which he has now made four albums of and which exposes a baritone player completely, since nothing is filling in the harmony behind him. Critics have consistently heard the same two things. Doug Ramsey wrote in JazzTimes that his tone gets bigger and his ideas more expansive from album to album, and All About Jazz's Francis Lo Kee placed him in that Payne, Parker, Adams, Chaloff and Brignola line and called him fluent in bebop's language. His own press biography adds a third quality that the records bear out: a strong and incisive wit, audible in the album titles as much as the playing.