Samurai Signaling Devices, Horagai, Conch Shell Horns.
 

Samurai Signaling Devices, Horagai, Conch Shell Horns.

Horagai（ほら貝） were used as signaling devices in times of battle. The samurai trained to use the horn was
called a Kai Yaku, and would carry it in a webbed net. Conch shell horns from other regions around
the world can only produce a single pitch, however Japanese conch shells can produce 3 to 5 different
notes. The pitch differences are attributed to the mouthpiece made of bronze or lacquered wood.

The Yamabushi, mountain ascetics, also used horagai, however their shells feature just 3 turns.
Samurai used 3 and a half turned shells. Yamabushi were often hired by daimyo to act as Kai Yaku
on campaigns, as their numbers would infer to an enemy that a much larger army was ahead.