soft-pedal

Meanings

1. To reduce the volume of (music, a sound, etc.).
2. To reduce the force or impact of (something); to damp, to mute; especially, to minimize the less desirable aspects of (something); to play down, to tone down.
3. To attempt to persuade someone about (something) through understatement, so that the listener accepts the good points as obvious.
4. Chiefly followed by on: to act in a less assertive or forceful manner.

Etymology

From soft pedal (“leftmost foot-pedal on most pianos which, when pushed, dampens the strings and so softens the note played”, noun).