諧 consists of 言/speak - here functioning as signific or determinative¹, and 皆/everybody, which functions as phonetic.² However, 皆 also conveys relevant meaning.³

Schuessler has early meanings for 皆/喈: “... ‘Be together with, agree , all’ [Shi]; ‘be or do in unison’ [Shi]”. Subsequently he writes that both 偕 and 諧 are etymologically to 皆/喈. “偕 ...‘Together’ [Shi]” and “諧 ...‘Be concordant, harmonious’ [Shi].⁴

I take this to mean that the graph 諧 was created for an extended or special meaning of 皆/喈, which would explain why 言/speak was added as signific.

The original graph 皆 consists of two people accompanying or following each other, and an element that has not been identified with complete certainty, though many scholars seem to think that it is a corruption of 曰/say.⁵ This element was already at the seal characters stage standardized as 白 (strictly meaning “white” but really an empty element that does not contribute meaning).

The top element 比 shares its origin with 从 (modern Japanese 従). At the earliest stage (oracle bone inscriptions) it was used for “accompany” or “follow,”⁶ which seems to lead up nicely to Schuessler’s meanings for 皆, “be together with,” “in unison” etc. The subsequent “be concordant, harmonious” covered by 諧 is not far from that either. If 白 really was 曰/say then that would have added a verbal aspect to 皆, as does 言/speak to 諧 (speak/sing in unison/harmony).

In making a mnemonic one can go several directions. One is for example to take 皆/everybody as a known, indivisible element. Another way is for example analyzing 皆 as 比/compare and 白/white.

Mnemonic: Speech can be like white noise, which is comparatively harmonious.