sound of bells and drums
鍠 centers on the resonant sound of metal percussion instruments, specifically bells and drums.
鍠 combines 金 (metal) with 皇, which likely contributes the sound and possibly an idea of grandeur or resonance, to express the sound of metal instruments like bells.
The left side is metal 金, and the right side 皇 suggests something grand. Imagine a grand metal bell being struck, producing a deep resonant sound.
For コウ, picture a large bell being struck and the sound echoing: kou — コウ. The deep metallic ring matches the kanji's meaning.