sing, recite, carol, poem, tanka, slander, defame
謌 centers on vocal expression through song or poetry: singing, reciting, or composing tanka. The slander/defame sense is a darker extension of using words to spread something, but the core is artistic vocal performance.
謌 combines 言 (words, speech) with 哥, which likely contributes the sound and is associated with singing or vocalizing. It is a variant form of 歌, where 欠 (open mouth) is replaced by 言 to emphasize the verbal aspect.
Words 言 on the left and a singing shape 哥 on the right: picture someone reciting a poem aloud, their words flowing like a song.
For カ, imagine a car with a loudspeaker driving by, reciting a poem: car -> カ, and the words 言 carry the tune.