The song most often associated with the cancan, and one that Morlacchi occasionally used with her troupe, is Jacques Offenbach's Galop Infernal, from his Orpheaus in the Underworld operetta. Like many classical pieces, it's a name that might not seem familiar, but a song you know immediately.
But Morlacchi didn't use the Offenbach tune when they first premiered the Cancan in December of 1867 at Boston's Theatre Comique, where she appeared in The Devil's Auction with Jon DePol's "Grand European Star Ballet Company," which billed her as "The Star Danseuse of the World."
There, Morlacchi used another piece, by Italian composer Petro Giorza. Signora Giorza had been in London with Morlacchi in the mid-1860s, and composed music for and conducted the orchestra at Her Majesty's Royal Theatre, where Morlacchi was prima ballerina. Giorza composed the music to a new ballet based on Harriet Beacher Stowe's book Uncle Tom's Cabin. Morlacchi had starred as Anglica, the "genius of justice." Both were natives of Milano, where Giorza was famous for his composition La Bella Gigogin, a fiercely patriotic song that quickly became an anthem to the proud people of Milan. Milan, in the Lombardy region of present-day Italy, had been a part of the Kingdom of Lombardy–Venetia, but was yearning to join an independent and unified Italy. The song's lyrics reflect the struggle:
Rataplan, I hear the drums
Calling me to the flag
Oh! what joy, oh! what happiness
I'm going to war
Rataplan, I'm not afraid
of bombs and cannons
I go trusting my fortune
That what will be will be.
Morlacchi and Giorza struck up a friendship in London that continued when the pair separately arrived both in America and in New York City at around the same time.
In America, Morlacchi starred in The Devil's Auction at Banvard's Opera House in October of 1867 while Giorza conducted the orchestra at the Academy of Music, just over a mile away. When DePol moved his troupe and their show to the Academy of Music on December 3rd, Morlacchi asked her friend if he could provide a piece for an upcoming performance. He jumped at the chance. Within months of the premiere of Morlacchi's Cancan later that month in Boston, sheet music had been printed and was selling across the country.
The song, which likely hasn't been played or heard in the over 150 years since it was premiered, exists now only as sheet music. As no recording exists, it is impossible to know exactly what the song sounded like as Morlacchi and her troupe bounded on stage and performed the Cancan dance, but because the sheet music survives, we can come pretty close.