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.
Alessandro Guidoni
Guidoni served in the Italo-Turkish War of 1911-1912 as a pilot trainee, soon achieving a full certification and flying "hydroplanes" (seaplanes). He then started studying weaponry and developed a new gyroscope-guided bomb to be delivered by planes against distant targets. In 1912, as a captain, he experimented with the air-launching of torpedoes by dropping weights from a Farman biplane. He also drew the plans of the seaplane carrier "Europa", which entered service with the "Regia Marina" (Italian Royal Navy) in 1915.