Marcello Giuliani was born on September 4, 1967, in Avezzano, in the Abruzzo region of Italy. He started on classical guitar before turning his focus to bass, later also picking up mandolin, banjo and double bass, and cites Marcus Miller and Jaco Pastorius as the players who shaped his own electric-bass sound. His professional career, however, has been built almost entirely in Switzerland and France: he joined pianist Malcolm Braff's trio in 1991, and in 1992 co-founded the Lausanne-based group Silent Majority, a multicultural project blending African and jazz-influenced grooves with multilingual rapping in English, Spanish, French and Swahili.

That same year, 1992, he began working with trumpeter Erik Truffaz, recording the quintet's first session, Niña Valéria. He became a permanent member of Truffaz's band from 1997, and has stayed in that chair ever since, close to thirty years running. The quartet's run of albums on Blue Note - Out Of A Dream (1997), The Dawn (1998), Bending New Corners (1999, certified Silver in France), The Mask (2000), Revisité (2001, a remix collection), Live In Jerusalem and The Walk Of The Giant Turtle (both 2003), Arkhangelsk (2007) and In Between (2010) - built the sound now generally filed as nu jazz or "future jazz": Truffaz's trumpet over Giuliani's bass, Marc Erbetta's drums and, in the earlier records, Patrick Muller's keyboards (Benoit Corboz from 2010). On The Mask, Discogs' own credits list Giuliani playing both acoustic and electric bass, producing, and co-writing seven of the album's eleven tracks. In 2000, alongside his work with Truffaz, he also recorded 3io 4tet for the Swiss label Altrisuoni, a trio with Malcolm Braff on piano and Pascal Portner on drums - his only own-name Discogs credit not billed under the Truffaz name. Truffaz's quartet, under various lineups including drummer Arthur Hnatek, has continued to record with Giuliani in the bass chair through Doni Doni (2016, featuring Malian singer Rokia Traore and French rapper Oxmo Puccino) and the two-part project Rollin' and Clap! (2023), on which he is credited as producer and co-producer as well as bassist.

Alongside the Truffaz quartet, Giuliani has built a substantial second career as a session bassist and record producer within French and Swiss popular music, honestly a competing identity worth naming directly rather than folding into the jazz story above. He has recorded or toured with Jane Birkin, Françoise Hardy, Sylvie Vartan, Henri Salvador, Lou Doillon, Stephan Eicher and Ben Sidran, and has been the touring bassist for singer Etienne Daho since at least 2018, including a Daho date at the Montreux Jazz Festival that year. As a producer, his best-known outside credit is Sophie Hunger's 2008 debut album Monday's Ghost, a number-one seller in Switzerland, recorded at Studio du Flon in Lausanne and the ICP Studio in Brussels; he has also produced for Anna Aaron and the Young Gods. Since at least the 2010s he has taught bass in the Contemporary Music ("musiques actuelles") department of the Haute Ecole de Musique (HEMU) in Lausanne, a pop- and rock-oriented teaching post rather than HEMU's separate jazz department. In 2018 he won the Swiss Music Prize (Schweizer Musikpreis), and he is listed as an associated artist of the Montreux Jazz Artists Foundation. All About Jazz maintains its own artist page for him, and Discogs' own genre tags for every one of his real own-name/co-billed Truffaz recordings run Jazz alongside Electronic, with the styles field consistently reading Future Jazz, Contemporary Jazz, Acid Jazz and Smooth Jazz.

Giuliani's playing sits at the foundation of what Erik Truffaz's quartet made into a genre unto itself: a trumpet-led, bass-and-drums-driven sound that runs trip-hop and drum'n'bass rhythm programming through an acoustic jazz band, closer in spirit to Miles Davis's electric period than to any dance-music scene, even though many of the quartet's tracks were licensed onto electronic and DJ-mix compilations through the late 1990s and 2000s (which is why a raw count of his Discogs credits skews toward Electronic, House and Trance tags that describe those compilations, not his own music). His own stated influences, Marcus Miller and Jaco Pastorius, point to a fusion-schooled, groove-first approach to the instrument, audible in his doubling between electric and upright bass across the Truffaz catalog and in the more straight-ahead, piano-trio setting of his own 3io 4tet session with Malcolm Braff. He plays guitar, mandolin and banjo as well as bass, and produces records for other artists as a parallel skill to performing on them. His parallel career as a session player and producer for French chanson and pop artists - Jane Birkin, Françoise Hardy, Etienne Daho and others - and his teaching post in HEMU's contemporary-music rather than jazz department are real, substantial, and openly part of his professional identity; they sit alongside, rather than displacing, the nearly three-decade jazz partnership with Truffaz that remains the anchor of his recorded work.