"with a positive mood," 1947, apparently from on the upbeat "improving, getting better," attested from 1934 and a favorite of "Billboard" headline-writers in the early 1940s, from the musical noun upbeat (1869), referring to the beat of a bar at which the conductor's baton is in a raised position; from up (adv.) + beat (n.). The "optimistic" sense apparently for no other reason than that it sounds like a happy word (the musical upbeat is no more inherently "positive" than any other beat).
例文
1. Neil 's colleagues say he was actually in a joking, upbeat mood.
ネルの同僚たちは、彼が実際に冗談を言っていて、気持ちがいいと言っています。
2.Scientists remain upbeat about the information that will be gathered.
科学者は収集される情報に希望を抱いている。
3.The Defense Secretary gave an upbeat assessment of the war so far.
国防長官は現在の戦争を楽観的に評価した。
4.The tone of the speech was upbeat .
今回の発言は非常に楽観的な口調だった。
5.The Chancellor 's upbeat message that the Government had licked infration for good was marred by more job losses.