to use a pedal on a piano while playing to make the sound softer (less loud);
e.g. In this section of the composition, the pianist might soft-pedal to reduce the volume of their playing.
(verb)
to present something as being less important than it actually is, to play it down or minimize it, often by not emphasizing its more unpleasant aspects;
e.g. They tried to soft-pedal the issue and pretend that things weren't as bad as they actually were.