Mantanus began a career as a pianist – noteworthy is his concert in the Sala Verdi in Milan with the Concertgebouw of Amsterdam; however, he quickly developed a passion for conducting which led him to study in Rome under the tutorship of Bruno Aprea as well as under Giuseppe Sinopoli, later becoming one of his assistants. During this formative period he attended numerous masterclasses, including with Jorma Panula (Schleswig-Holstein, Salzau) and Gianluigi Gelmetti (Accademia Chigiana, Siena). In 2009, Lorin Maazel invited him as a fellow to his Castleton Festival in Virginia, USA. Mantanus the became Maazel's assistant in Italy and in Washington D.C. for productions by The Petruzzelli Theatre of Bari. Maazel also appointed him as his associate conductor for the Castleton Festival.
In 2009, after four years working for The Symphony Orchestra of Milan Giuseppe Verdi, conducting outdoor and family-orientated concerts, Mantanus made his debut on the podium of the Orchestra della Svizzera Italiana. He also held the post of principal conductor for the Orchestra of the City of Ravenna for five years. He worked with numerous orchestras on a wide variety of productions including Cagliari's Teatro Lirico, Como Sociale Theatre with the Orchestra 1813, Filarmonica Toscanini, Pomeriggi Musicali at Milan's Dal Verme theatre and Tito Schippa's Orchestra in Lecce, and contemporary opera at Biennale Musica 2016 in Venezia.
Matthieu Mantanus holds a deep and enthusiastic commitment to musical innovation, and for increasing the accessibility of classical music to the general public. During the 2014-15 season he went on air in prime time on the Italian national TV channel RAI 3, leading the Jeans Symphony Orchestra - which he founded himself - in presenting five short concerts. And the formula worked. Audiences approached one million viewers per evening. The following year he presented for the sister channel RAI 5 a whole series of live broadcasts from theaters around Italy featuring the world and works of Italian theatre, included the prestigious La Scala Opening Night.
Matthieu Mantanus has also authored a number of books aimed at a broad public audience including Una giornata eroica - A Heroic Day - (Feltrinelli, 2009 - translated into Chinese and Korean), Beethoven e la ragazza con i capelli blu – Beethoven and the Blue Haired Girl - (Mondadori 2016 - translated into French under the title “Beethoven et la fille aux cheveux bleus”) and Rossini! (Feltrinelli 2018).
In 2013 he founded JeansMusicLab Productions to bring into life the innovative musical shows he has created: these include Revolution! (2014), Intimacy (2015-2016), BachBox (2018) and Baroque Reloaded (2019). The creation of the show BackBox saw Matthieu first experiment with electronic music. Here he discovered, elaborated and embraced a brand new sense of expression through a surprising and very personal musical language. In 2020 was published his second EP, Sound of elements. In 2021, he wrote his first work for (non amplified) orchestra, synths and electronic, This is no Mozart.
In 2020 Matthieu moved back to Switzerland after nearly 20 years abroad and founded the OpenStudio in his hometown, Aigle. In summer 2021, he programmed the first JeansMusic Festival in Apulia (Italy), presenting the crosspoint between classical and electronical creativities.