chant (esp. Noh), folksong, ballad
謠 centers on a sung or chanted piece, especially a traditional folksong or ballad, and by extension the chanting style used in Noh theater.
謠 combines 言 (speech, words) with 䍃, which likely contributes the sound and may relate to a rhythmic or shaking motion, together suggesting a sung or chanted piece.
Words (言) set to a rhythmic, swaying motion (䍃) become a song or chant. Picture a Noh performer chanting a ballad while swaying gently.
For ヨウ, imagine a folksong about a yo-yo: the yo-yo goes up and down while the singer chants 'yo, yo' — yo -> ヨウ.