Guidonian hand
In Medieval music, the Guidonian hand was a mnemonic device used to assist singers in learning to sight-sing. Some form of the device may have been used by Guido of Arezzo, a medieval music theorist who wrote a number of treatises, including one instructing singers in sightreading. The hand occurs in some manuscripts before Guido's time as a tool to find the semitone; it does not have the depicted form until the 12th century. Sigebertus Gemblacensis in 1105–10 did describe Guido using the joints of the hand to aid in teaching his hexachord. The Guidonian hand is closely linked with Guido's new ideas about how to learn music, including the use of hexachords, and the first known Western use of solfege.
The Black Hand (book)
Beginning in the summer of 1903, an insidious crime wave filled New York City, and then the entire country, with fear. The children of Italian immigrants were kidnapped, and dozens of innocent victims were gunned down. Bombs tore apart tenement buildings. Judges, senators, Rockefellers, and society matrons were threatened with gruesome deaths. The perpetrators seemed both omnipresent and invisible. Their only calling card: the symbol of a black hand. The crimes whipped up the slavering tabloid press and heated ethnic tensions to the boiling point. Standing between the American public and the Black Hand’s lawlessness was Joseph Petrosino – dubbed the "Italian Sherlock Holmes" he was a famously dogged and ingenious detective, and a master of disguise. As the crimes grew ever more bizarre and the Black Hand's activities spread far beyond New York’s borders, Petrosino and the all-Italian police squad he assembled raced to capture members of the secret criminal society before the country’s anti-immigrant tremors exploded into catastrophe. Petrosino's quest to root out the source of the Black Hand's power would take him all the way to Sicily—but at a terrible cost. Since the book was released, it was received acclaimed by critics. Author Mark Adams said: "The Black Hand is nonfiction noir at its best: a real-life Godfather prequel that pits an unforgettable Italian-American hero against the seemingly unstoppable menace that would become the New York mafia". Kirkus Reviews said it was: "A thrilling tale of the "Italian Sherlock Holmes"".