soft pedal
Synonym discussion
Sense: verb/1
All four expressions mean making something seem less important or serious, but they differ in formality and connotation. 'Downplay' is the most common and neutral — a manager can downplay risks without being dishonest. 'Understate' is more formal and deliberate; a scientist might understate a finding for caution. 'Play down' is the conversational phrasal-verb equivalent of downplay. 'Gloss over' carries a more negative tone — it suggests skipping past unpleasant details rather than just reducing their weight. For example, a politician might downplay a scandal by citing other achievements, but if the same politician glosses over the scandal entirely, listeners would feel misled.
Etymology
The noun 'soft pedal' comes directly from piano design — the left pedal that literally makes the sound softer. By the early 1900s, English speakers began using it as a verb metaphorically: to 'put the soft pedal on' something meant to dampen its force or importance, just as the pedal dampens the piano's sound. Over time the phrase shortened to the verb 'soft-pedal'.