In 1902 he traveled extensively throughout Europe; during this time he studied under Max Bruch in Berlin.
He first achieved note with a one-act opera, Uguale fortuna, which won a national competition.
His biggest success internationally was his 1916 arrangement of keyboard sonatas by Domenico Scarlatti for the Sergei Diaghilev ballet in The Good-Humoured Ladies (Le donne di buon umore).
It was he and Arturo Toscanini who completed Arrigo Boito's unfinished opera Nerone.
Tommasini was a leading figure in the revival of orchestral music in twentieth-century Italy.