reed flute
笳 refers to a reed flute, a wind instrument made from a reed or bamboo.
笳 combines 竹 (bamboo) with 加, which likely contributes the sound. The character refers to a bamboo reed flute.
The top 竹 is bamboo, and the bottom 加 looks like a mouth 口 blowing air with force 力. Picture a bamboo reed flute being played with added breath.
For カ, imagine a car horn that sounds like a reed flute: car -> カ, and the bamboo flute honks like a car.