下麦 comes from voice-chat platforms like 连麦 / 多人语音 rooms - Clubhouse-style audio and livestream 连麦 segments. 麦 = 麦克风 (microphone). The room has 麦位 (mic seats); going 上麦 takes a seat, 下麦 leaves it.
usage
Pair: 上麦 (take the mic / step on stage) ↔ 下麦 (leave the mic). Related: 抱麦 (hog the mic), 切麦 (mute the mic), 抢麦 (grab the mic), 麦序 (mic queue).
