He subsequently became interested in jazz. and became a member of the Hot Club in Lisbon. After having bass guitar lessons with António Ferro he started taking double bass lessons with David Gausden and playing in jam sessions; also took part in workshops with Rufus Reid, Niels Henning, Orsted Pederson, Eberhard Weber, among others.
As from 1984 he plays jazz and improvised music in Portugal and abroad with musicians such as António Pinho Vargas, Mário Laginha, João Paulo Esteves de Silva, Bernardo Sassetti, Benny Lackner, Carlos Martins, Tomás Pimentel, Maria João, José Peixoto, Tommy Halferty, John Wadham, Luigi Waites, Jarmo Savolainen, Jim Leff, Ralph Peterson Jr., Paolo Fresu, Andy Sheppard, Peter Epstein, David Binney, Ralph Towner, among others.
In 1990, Mário presented his first project based on original compositions which was awarded 1st prize for performance and 2nd prize for composition in the competition “A Juventude e a Música“ (Young People and Music).
Mário Franco has performed with many different musicians (jazz and classical music) in Europe and was part of some of Portugal´s most important music festivals.
In 2006 Tone of a Pitch Records edited his first record as a leader, “This Life”, with Jesse Chandler, André Fernandes, João Lencastre, João Gomes and NY based David Binney. This recording was reviewed, by the American magazine All About Jazz, one of the best CDs of 2006, as well as by the Portuguese newspapers Expresso, Público and the bimonthly magazine Jazz.pt.
Two years later Mário also worked as a dancer, musician and composer in the ballet “Come Together” by the choreographer Rui Horta for the National Ballet Company of Portugal (CNB). In December 2008 he composed the music of “Xirtam”, a ballet by the choreographer Xavier Carmo for the company Quorum Ballet and in 2009 he worked with the Early and Contemporary Music Consort “Seven Tears”. In the same year he composed music for a piece by the dancer and choreographer Alina Lagoas.
He currently continues his work as a sideman in the portuguese jazz scene and he started a new project featuring the musicians Julian Argüelles, Sérgio Pelágio, João Paulo and Alexandre Frazão.
Mário Franco is also a dancer from the National Ballet Company of Portugal since 1986.