Conversation so far:
Did the Manchu people create the Octagonal drum?
It is said that octagonal drum originated with the snare drum of the Eight-banner military and the melody was made by the banner soldiers.
What was the Octagonal drum used for?
Octagonal drum is a type of Manchu folk art that was very popular among bannermen, especially in Beijing.
What material was the octagonal drum made from?
The drum is composed of wood surrounded by bells. The drumhead is made by wyrmhide with tassels at the bottom.

Question: Why was the Octagon shape chosen for the drum?
Self-contained rewrite: Why was the Octagon shape chosen for the drum?