節
ふし · fushi · JLPT N3 · noun
tune
🎋🎵 竹 bamboo on top: joints split a bamboo stalk as phrases split a tune
節 originally meant the joint or node on a bamboo stalk. Those joints cut the stalk into regular sections, and the word came to mean sections of a song too: a melody, its tune and tone. A knob in wood or a knuckle is the same kind of joint.
せつ · setsu · JLPT N3 · noun
when
🎋 竹 bamboo on top: bamboo joints split a stalk into neat sections
節 first meant a bamboo node, the ring that splits the stalk. That gives section, clause (a section of a sentence) and season (季節 kisetsu, a section of the year). その節 means at that point in time, which gives when. Hook: setsu sounds like a set section.