Háizi chúnzhēn de xiàoróng chùdòng le zàichǎng měi yī gè rén de xīnxián.
The child's innocent smile touched the heartstrings of everyone present.
Tips
usage
心弦 is typically used with verbs like 拨动 (to pluck), 触动 (to touch), or in the set phrase 扣人心弦 (grasping at the heartstrings — meaning thrilling or captivating).