Michael Supnick was born in Worcester, Massachusetts, on July 13, 1962. He started on trombone at ten, played in theater-orchestra pits through high school on shows including Show Boat, Guys and Dolls and Carousel, and at seventeen began sitting in at his first jam sessions with local jazz musicians. He went on to study at Indiana University in Bloomington under jazz historian and educator David Baker, then completed his training at Berklee College of Music in Boston, graduating with honors in Professional Music under trombonist Phil Wilson, arrangers Herb Pomeroy and Bob Freedman, and ensemble director John LaPorta.

In 1986, at twenty-four, Supnick moved to Italy, where he has lived and worked continuously ever since, settling in Rome and building the whole of his professional career there. He became a specialist in New Orleans jazz, Dixieland and swing, and from 1994 to 1997 served as lead trombonist of the Italian Big Band, whose recordings from that period are Discogs-tagged Jazz. In 1996 he founded his own group, the Sweetwater Jazz Band, whose debut Classico Jazz . I Fantastici Anni '20 (1997, Libera Informazione Editrice) is Discogs-verified as a Main-artist release. His own leader album, Un Americano A Roma (2021, Helikonia) - the title translates as "An American in Rome" - is his only other Discogs Main-artist credit, drawing on four different ensembles he leads or co-leads: the Michael Supnick Classic Quartet, the Michael Supnick Modern Quartet, the Sweetwater Jazz Band, and Lino Patruno Jazz Show & His Blue Four.

Much of Supnick's four-decade recorded output sits inside the orbit of guitarist and banjoist Lino Patruno, the central figure of postwar Italian Dixieland. Discogs credits Supnick on trombone alongside Patruno and violinist Mauro Carpi on "Bix & All That Jazz" (1998, Lino Patruno & The Red Pellini Gang), a Bix Beiderbecke-repertoire session with an introduction by the Italian film director Pupi Avati. He plays clarinet on Jammin' For Condon (2002, Lino Patruno & His All Stars), recorded live at the Ascona Jazz Festival in Switzerland alongside American trad-jazz veterans Ed Polcer, Dan Barrett, Tom Baker, Jim Galloway and vocalist Rebecca Kilgore, with pianist Rossano Sportiello and clarinetist Evan Christopher also on the bill. He returns on trombone and flugelhorn for the Red Pellini Gang's Minnie Minoprio (2003), on trombone for the undated compilation Soundtracks (Lino Patruno, on the track drawn from the theatrical production La Signora in Blues, alongside Carpi), and on trombone again as a "Special Guest" for the tribute record Remembering Spiegle (Lino Patruno & The Red Pellini Gang, honoring trombonist Spiegle Willcox). On the undated compilation Lino Patruno Presents A Tribute To Bix Beiderbecke (2004), Supnick is credited on vocals alongside a lineup that includes guitarist Howard Alden, confirmed via the same release's Discogs credits.

Supnick was also a founding member of the ensemble The Ghosts Of The Twenties, credited on trombone and cornet on the group's self-titled 1996 release (Riviera Jazz Records), and plays trombone on Carpi's own-name session Stringin' the Blues (2002, billed to Mauro Carpi & Friends), where he shares the frontline with Spiegle Willcox. On singer Larry Franco's All Of Me (2008, Philology), Supnick's trombone sits alongside tenor saxophonists Daniele Scannapieco and Michele Carrabba and guitarist Guido Di Leone; he is also a Discogs-verified member of the separate Larry Franco Jazz Society, whose A Crooner In The Land Of Dixie (2007, Philology) is a further group billing. His trumpet and trombone appear on two tracks of the various-artists blues session Back To Life (2010, Jona's Blues Band), where he also arranged the horns, on a session that features vocals from Italian entertainer Renzo Arbore; a separate, brief Renzo Arbore connection runs through the compilation Per Amore (2006), where Supnick plays trumpet on the track "Quando Una Ragazza A New Orleans" with the group Renzo Arbore E Swing Maniacs, and through two later TrackAppearance credits for the same song, "Blue Christmas," on Arbore's ...E Pensare Che Dovevo Fare Il Dentista... (2014) and Arbore Plus (2017) - Discogs-tagged Pop and Folk, not part of Supnick's jazz identity. His most recent Discogs-documented session credit is trumpet and trombone on Taffetà (2021, MarteLabel), a pop record by vocalist Luiza Constantin.

Beyond performing, Supnick appeared onscreen as a trombonist in Giuseppe Tornatore's The Legend of 1900 (1998), and provided trumpet performances and an acting role in Franco Nero's 2005 film Forever Blues, whose score was composed by Lino Patruno with violin contributions from Mauro Carpi. He has also published trombone instructional material and a work of narrative fiction, Passing Moments, set in 1967. His own site and Spotify list a considerably longer catalog beyond what Discogs indexes by title, including Supnick Swing'n... Dixie, Real Book Beyond Easy Jazz Lessons, Vol. 1 (with guitarist Michele Ariodante), Michael Supnick and Sweetwater Jazz Band, Vol. 1 (Live) (2011), Top Jazz Standards, American in Paris, American in Naples, Trumpet and Piano and a Christmas Album; Wikipedia's entry for Supnick totals his self-reported output at 97 releases (52 studio albums, 16 live albums, 29 compilations and 4 audiovisual works), a figure not independently itemized here.

Supnick's core identity is New Orleans jazz, Dixieland and swing trombone and trumpet in the American hot-jazz revival tradition, the same idiom Lino Patruno spent his career putting in front of visiting American originators. Supnick's own version of that role reverses the direction: he is the American voice inside Italian-led trad-jazz ensembles, whether as a founding member of The Ghosts Of The Twenties, the lead trombone chair of the Italian Big Band, or a recurring sideman across Patruno's and Carpi's overlapping bands. His own Sweetwater Jazz Band and his sole leader album, Un Americano A Roma, both work the same repertoire: the tracklist of the latter runs through "Doctor Jazz," "Take the 'A' Train," "Bye Bye Blackbird," "Stardust" and "The Sheik of Araby," standards squarely in the Dixieland and swing songbook. A smaller thread of his career, playing trumpet on a Renzo Arbore vocal session and a Luiza Constantin pop record, sits outside jazz entirely and is not part of his core identity.