Several parts combine into one character.

調 is a phono-semantic character: 言 (speech) for meaning and 周 (all around) for sound. Bringing speech (言) into even balance all around (周) gave "to tune, to adjust, a melody, to investigate." The sense of 周 (reaching everywhere) resonates faintly too.

The simplified form is 调, with 言 reduced to the speech radical 讠 — the form splits by mode.

Korean hanja-sound "jo": 調査 (josa, investigation), 調節 (jojeol, adjustment), 調和 (johwa, harmony), 强調 (gangjo, emphasis), 順調 (sunjo, smooth progress). The melody / key of music (長調 major, 短調 minor) is also this character.

Mandarin: diào, 4th tone (melody, investigate) / tiáo, 2nd tone (to make even, adjust). 调查 (diàochá, to investigate), 声调 (shēngdiào, tone), 调动 (diàodòng, to transfer) / 调节 (tiáojié, to adjust), 空调 (kōngtiáo, air conditioner), 调皮 (tiáopí, naughty). A one-character, two-tone case — "investigate / melody" is diào (4th), "adjust" is tiáo (2nd). 空调 (air conditioner) reads tiáo.

Japanese: on-reading チョウ (chō), kun しら.べる (shiraberu) and ととの.える (totonoeru). 調査 (chōsa, investigation), 調子 (chōshi, condition / form), 調節 (chōsetsu, adjustment), 順調 (junchō, smooth), 体調 (taichō, physical condition). 調べる (shiraberu, to investigate) is a daily Japanese essential.

Memory aid: bringing speech (言) into even balance all around (周) — to tune, to harmonize, to investigate.