Quick word of the week today, and musical, since I just finished writing A Song Unheard. 😉
In today’s vernacular, upbeat means “with a positive mood”–but this is a rather modern connotation, only dating back to about 1947. It’s thought to have come from the phrase on the upbeat, which meant “improving, getting better.”
This does indeed come from the musical idea that a conductor’s baton is raised during a given beat in a measure (the denotation which is also rather modern, dating only to 1869)–however this beat in a measure isn’t particularly positive by nature or anything. It gained a “happy” connotation simply because it sounded optimistic. My kind of reasoning, LOL.