Antonyms of adj low-key

1 sense of low-key

Sense 1
low-key, low-keyed, subdued -- (restrained in style or quality; "a little masterpiece of low-keyed eloquence")

INDIRECT (VIA restrained) -> unrestrained -- (not subject to restraint; "unrestrained laughter")

Similarity of adj low-key

1 sense of low-key

Sense 1
low-key, low-keyed, subdued -- (restrained in style or quality; "a little masterpiece of low-keyed eloquence")
       => restrained (vs. unrestrained) -- (under restraint)