Massimo Nunzi was born in Rome on May 25, 1962. He came up as a jazz trumpeter through the city's festivals, clubs and theaters in the 1980s and 1990s, sharing stages with Don Cherry, Lester Bowie, Dizzy Gillespie, Toshiko Akiyoshi and Gianluigi Trovesi, among others. In 1987 he founded his first large ensemble, the Orchestra Trombe Rosse, and by 1991, at 29, he was already conducting the RAI orchestra for Italian state television.

His Discogs-documented recording history opens in 1989 with the library-music LP Strumentali: Summer Voyage, credited alongside Mauro Dolci, and continues through a 2000 film soundtrack, Le Sciamane, for which he wrote both music and lyrics. His first release tagged as jazz on Discogs is Casamoderna (2003, Abeat Records), co-billed with drummer Roberto Gatto and featuring saxophonist Mauro Negri, bassist Gianluca Renzi, trombonist Luca Begonia, trumpeter Giovanni Amato and vocalist Ada Montellanico. In 2004 he conducted the debut concert of the Orchestra Nazionale Italiana del Jazz (the Italian National Jazz Orchestra) at the Universal Jazz Expo in Genoa, covered at the time by All About Jazz.

Nunzi has built his career primarily as an orchestra leader, arranger and composer rather than as a small-combo soloist. In 2014 he founded the Orchestra Operaia, whose 2016 self-titled album on Casa del Jazz, Rome's dedicated jazz institution, drew explicitly on the big-band writing of Gil Evans and the stylistic range of Frank Zappa; Nunzi is credited as arranger, music director, transcriber and electronics player, and also plays trumpet on the record, alongside vocalists Marta Colombo, Petra Magoni and Chiara Morucci and a young arranging team billed as the Lone Arrangers. In 2018 he founded a further ensemble, the Orchestra Observatorium, and that same year served as conductor and producer, alongside conductor Tonino Battista, on The Nearness of You (Unit Records), a big-band session led by the veteran Swiss-Italian flugelhornist Franco Ambrosetti. Pianist Domenico Sanna played piano and keyboards on that same session.

Jazzit magazine's readers voted Nunzi Italy's top arranger in both 2014 and 2015, and in 2016 he was included in La Repubblica's "Jazz Italiano Live" collection alongside a group of prominent Italian jazz musicians that reportedly included Paolo Fresu and Stefano Bollani; this profile could not independently verify the full artist list beyond secondary accounts. He has also worked extensively outside pure jazz performance: he wrote the score for a 2004 Mastercard advertisement that won Top Brand Advertising honors that year, created and toured the interactive concert format "Jazz: istruzioni per l'uso" ("Jazz: Instructions for Use"), which sold out runs at Rome's Teatro Sistina in 2005 and 2006 and became a twelve-part television documentary and a companion book published by Laterza, and has scored television series and films, including Netflix's Gli infedeli.

From 2019 to 2023 Nunzi directed the Jazz Campus Kids Orchestra at Rome's Auditorium Parco della Musica, an education-focused ensemble for musicians aged 8 to 18, and by 2026 he continued to lead its successor, the Jazz Campus Orchestra, in residence at Casa del Jazz, including a performance for International Jazz Day Roma 2026. Some accounts of his early career also describe him performing alongside pianist Enrico Pieranunzi (an unrelated musician despite the similar surname), though this profile found no Discogs recording credit connecting the two directly.

Nunzi's core identity is as a big-band and orchestra leader rather than a small-group soloist: from the Orchestra Trombe Rosse (1987) through the Orchestra Operaia (2014) and the Orchestra Observatorium (2018), his own catalog runs almost entirely through large jazz ensembles he founded and arranged for himself. The Orchestra Operaia project named Gil Evans's orchestral writing and Frank Zappa's stylistic freedom as explicit reference points, and its vocal features in English, Latin, German and Portuguese show a composer working across idioms rather than inside a single jazz subgenre. That same range carries into his work outside the concert stage, in advertising, television and film scoring and in "Jazz: istruzioni per l'uso," an audience-facing format built to teach jazz history and language to non-specialist listeners, which places him as much in the role of jazz educator and popularizer as performer.