At the age of 20 he won a competition to gain the position of piano professor at the Royal Conservatorio of San Pietro a Majella in Naples.
Although he was considered a great interpreter of J. S. Bach, Beethoven, Schumann and Chopin, he was also a champion of old Italian music.
When Anton Rubinstein was appointed director of the Petrograd Conservatory, he invited Cesi to direct the pianoforte schools there.
His educational writings (Method for Pianoforte) had considerable importance, and he wrote many volumes of revision of piano music.
Sigismondo co-founded the Liceo Musicale, a private music school, in Naples in 1908 with Ernesto Marciano, gave concerts in many parts of Italy, and became a well-known teacher.