row or file of dancers
佾 refers to a row or file of dancers, specifically in a ceremonial or ritual context. The meaning is narrow and concrete, with no strong abstract extensions.
佾 combines 亻 (person) with 䏌, which likely contributes the sound and relates to the idea of a row or file. The exact historical development of 䏌 is uncertain.
A person 亻 beside 䏌, which looks like a row of dancers lined up with their arms raised. Picture a ceremonial dance formation.
For イツ, imagine a row of dancers moving in unison to a beat: "itsu" sounds like "it's you" leading the dance. The rhythm cues イツ.