bugle
箛 centers on a specific type of wind instrument: a bugle, likely made of bamboo.
箛 combines 竹 (bamboo) with 孤, which likely contributes the sound. The character refers to a bamboo wind instrument, consistent with the bamboo radical.
Bamboo 竹 on top of 孤 suggests a solitary bamboo tube used as a bugle.
For コ, imagine a lone bugler playing a note that sounds like 'co': co -> コ, echoing from the bamboo instrument.