The metaphor comes from ancient lyric: wife as 琴瑟 (qin and se — paired stringed instruments). Losing one's wife was 断弦 (broken string); taking a new wife was 续弦 (re-stringing).
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Literary/formal, and strictly used of widowers, not widows or divorced men. Second sentence shows it can be negated for widows too, but the gender-specific nuance lingers. Everyday speech just uses 再婚.
