Guido Mazzon was born in Milan in 1946 and has been one of the leading trumpeters of Italian free jazz since the early 1970s. He studied trumpet with Alvaro Persenico, first trumpet of the orchestra of La Scala, after starting on clarinet, and took a degree in biological sciences. He is a cousin of the film-maker and poet Pier Paolo Pasolini (his grandmother was the sister of Pasolini's mother), and the trumpet is part of that story: in the summer of 1957, at Casarsa, the eleven-year-old Mazzon showed Pasolini an old cylinder-valve trumpet, and Pasolini gave him money to buy a new silver one, a gesture Mazzon later described as a passing of the witness. He told it in La tromba a cilindri: La musica, io e Pasolini (2008), written with the philosopher Guido Bosticco and published with an audio CD.

Biographical summaries date his first jazz playing to 1964, in a traditionalist student band, followed by private composition studies from 1967 and an interest in free jazz. In 1970 he founded the Gruppo Contemporaneo, which drew younger Milan players; summaries name the tenor saxophonist Daniele Cavallanti, the bassists Attilio Zanchi and Roberto Del Piano, the pianist Gaetano Liguori and the drummer Filippo Monico among its members. Discogs documents part of that circle: Cavallanti plays tenor saxophone on "Uffa!" on Mazzon's 1975 album Ed Ora Parliamo Di Libertà, and Liguori's own biography places him in the group from 1971. His first record under his own name, Gruppo Contemporaneo (PDU, recorded April 22, 1974), is a trio with the bassist Daniele Ruffa and the drummer Giampiero Prina. The Quartetto Di Guido Mazzon, with the altoist Edoardo Ricci, the bassist Roberto Bellatalla and the drummer Tony Rusconi, made Ecologia (1975) and appeared live at Milan's Università Statale in November 1975 on the compilation Nuove Tendenze Del Jazz Italiano. His Milan-based Precarious Orchestra, with Mark Charig, Radu Malfatti, Renato Geremia and Bruno Marini alongside Rusconi, was one of the few Italian groups to play Germany's Moers festival, in 1978.

The 1970s brought a run of records on the Milan labels PDU and L'Orchestra. Ed Ora Parliamo Di Libertà is described in Discogs's release notes as his first album outside a group and a socially engaged work; Solo (Una Rotella E Una Vitina) was recorded in Lugano in October 1975, and includes a "Tema Per Il 'Che'". Duetti Duets (1976) paired him with the percussionist Andrea Centazzo, recorded at Centazzo's studio in Moruzzo with no overdubs, and the two kept returning to the format for decades. Cliché (1976) is theatre music made with the rock band Stormy Six and Rusconi; Gospel (1977) is a duo with the saxophonist Mario Schiano; and Songs & Tales (1979) sets his trumpet, flugelhorn and piano against the voice of Marco Magrini reading texts by Leonardo da Vinci, James Joyce, Plato, Charles Dickens and Ludovico Ariosto. Meanwhile he was working as a section player: in March 1973 he was one of two trumpeters, with Enrico Rava, on Giorgio Gaslini's Message (BASF), a session that also included Gianni Bedori, Danilo Terenzi, Massimo Urbani, Franco Tonani and Bruno Tommaso; in February 1976 he sat in the front line of Liguori's Collective Orchestra with Urbani and Terenzi; and in 1975 he was co-billed with Gaslini, Bedori and Liguori on the PDU double LP Il Nuovo Jazz Italiano Degli Anni 70.

In the 1980s and early 1990s he worked across Europe's improvising scene. He is credited on the King Übü Örchestrü's Music Is Music Is ..., an all-improvised set recorded at the Akademie der Künste in Berlin on December 22-23, 1984. The Unrepentant Ones (Fonit Cetra, 1986) is a totally improvised session recorded in Rome for RAI on February 17, 1986, billed to Mazzon, Giancarlo Schiaffini, Schiano, Geremia, Tommaso and Rusconi. Effetti Larsen (Splasc(h), 1988) documents a March 4, 1988 concert in Rome with Schiano and the Liguoris, father and son. Other Line (1990), with the pianist Umberto Petrin and the drummer Tiziano Tononi, was recorded at Milan's Barigozzi Studios with Giancarlo Barigozzi as sound engineer, and Il Profumo Della Libertà (1992) was recorded direct-to-DAT at the same studio with Ellen Christi, Geremia, Eleonora Nervi, Petrin and Tononi named on the cover.

The Italian Instabile Orchestra has been the steadiest large-ensemble home. Biographical accounts call him a founding member who contributed pieces to its repertoire, and the Pasolini study centre dates his membership to 1990. Discogs credits him on trumpet and flugelhorn on ten of its records and films from Live In Noci And Rive De Gier (1992) to Il Suono Instabile Della Libertà (2010), among them the ECM album Skies Of Europe (1995), Gaslini's Masks (1992), The Owner Of The River Bank (2003), recorded live at the Talos Festival in Ruvo di Puglia on September 10, 2000 with Cecil Taylor, and Creative Orchestra (Bolzano) 2007 with Anthony Braxton, recorded at the Alto Adige Jazz Festival on June 16, 2007. His orchestra colleagues on those records include Gianluigi Trovesi, Paolo Damiani, Pino Minafra, Eugenio Colombo, Carlo Actis Dato, Alberto Mandarini, Cavallanti, Schiaffini, Tommaso and, from 2000 on, Giovanni Maier; Rava and Antonello Salis are credited as guests on Litania Sibilante (2000).

Outside the orchestra his 1990s records show a chamber-music side. Trumpet "Buzz" Duo (Splasc(h), 1996) is a two-trumpet record with Mandarini, taken from concerts in Rome, Terruggia and Mulhouse in 1994 and 1995. On Awake Nu (A Tribute To Don Cherry) (1996) he plays trumpet and flugelhorn in Tononi's band with Cavallanti and Maier. If (1998), recorded at Obelix Studio in Legnano, sets his trumpet against the tubist Michel Godard, Petrin's piano and the voice of Maria Elena Moro, with words and music by Mazzon. He was a featured soloist beside Evan Parker, Godard and Geremia on Pasquale Innarella's Pirotecnie Sonore, recorded at the Orsara Music Festival in 1997, and played on Francesco Branciamore's Improvisation Of The Four Seasons, from the Siena Jazz Festival that year, with the trombonist Paul Rutherford and Godard.

The 2000s are the most documented decade. Come Un Soffio Di Vento (2000) is a trio with the pianist Beppe Grifeo and Rusconi that takes in two Sun Ra pieces and Bill Evans's "Peace Piece". With Maier he made two trumpet and double-bass duo records for Palomar, Drops (2005) and Entropia (2009). When We Were Kings (Soul Note, 2005), a trio with Liguori and Andrew Cyrille, takes Muhammad Ali's 1974 fight in Kinshasa as its subject. Our Prayer (Splasc(h), 2005) is a Cavallanti and Mazzon quintet and septet recording with Maier, Tononi, Schiaffini and others. For Ictus Records he and Centazzo assembled the Double series, released in 2006-2007 from sessions made between 1976 and 2007; Ictus also put out Flights Of Fancy (2007), a five-movement piece recorded at Noci on June 25, 1993 by the Guido Mazzon Sextet with Rutherford, and the anthology As The Crow Flies (2008), whose cover names Lester Bowie, Cyrille, Godard and Christi among its guests and which The Free Jazz Collective rated four and a half stars.

Since 2013 most of his records have come from Setola Di Maiale. Il Tempo Non Passa Invano (2013) is a duo with the bassist Roberto Del Piano; Apro Il Silenzio (2014), with the group One Lip 5, has him and Mandarini on trumpets beside the guitarist Claudio Lodati and the violinist Emanuele Parrini. With the clarinetist Marta Sacchi he made Sounding Lines (2017) and The Land Of Blue Lichens (2018) as the Neu Musik Duett, and with Sacchi and the percussionist Stefano Giust, Neu Musik Projekt (2015), which The Free Jazz Collective rated four stars. In July 2022 he was one of nineteen players at Andrea Centazzo's four-night Ictus festival at Milan's Teatro Out Off, released in 2024 as the box set Ictus@45 - Out Off Nights.

Mazzon's playing sits between a classical trumpeter's training and the open forms of free improvisation. His teacher Persenico was a first trumpet of La Scala, and a Free Jazz Collective review of As The Crow Flies praises how easily he moves from very classical sounds to avant-garde ones and everything in between; the same site's review of Neu Musik Projekt singles out his confident voice and agile phrasing. Discogs tags 39 of his 79 release and master entries Free Jazz, 37 Free Improvisation and 38 Contemporary Jazz. The music is often written to a theme or a cause: the titles Ed Ora Parliamo Di Libertà and Il Profumo Della Libertà, a "Tema Per Il 'Che'" on Solo, a record for two theatre productions, and readings of Joyce and Plato on Songs & Tales. He also plays piano, clarinet, flugelhorn, cornet and small instruments and toys on his own records, writes his own liner notes, and returns often to the duo, whether with a drummer (Centazzo), a bassist (Maier, Del Piano), a second trumpet (Mandarini) or a clarinetist (Sacchi). Biographical summaries of the Gruppo Contemporaneo stress its theatrical, ironic side, close to the Dutch strand of European improvisation. His tribute to Don Cherry on Awake Nu, and his recording of Sun Ra and Bill Evans pieces on Come Un Soffio Di Vento, mark two of the figures he has openly played through.