木箱鼓

• ⺮(bamboo)RADICAL
• 相(look at each other; support)PHONO-SEMANTIC

A bamboo box or trunk with two opposite sides facing each other looks like the character for "mutual" or "each other."

• 壴(drum on stand (iconic form))RADICAL
• 支(branch; handle of a mallet)ASSOCIATIVE

A hand holding a stick strikes a drum resting on a stand to make the sound of a drum.