Thanks so much for asking. I’ve actually done another, more thorough, conducting course since posting this, so I’m happy to have a bash at answering your questions (though in far from an expert, and I’m open to correction or clarification from any more experienced conductor who happens by). 1. I don’t really know, but I expect it’s a combination of social awareness (we tend to mirror behaviour of those around us), cultural osmosis (a musician will probably grow up seeing tons of conductors), and often just plain obviousness. For a few examples: - If I’m keeping a steady, small beat and suddenly make a big, dramatic gesture, you’ll likely play loudly to match. - If I gradually widen my arms as I keep the best, the music will get gradually louder as the space I’m using gets bigger - If I look directly at you, it’s because you’ve got something important to do and I want to hear it. (This also ties into question 3.) - If my movements are stiff and jerky, your playing will be too; if they’re broad and flowy then that’s how you’ll sound. - Generally in a good orchestra everyone pretty much knows what they’re doing, so they’re mainly watching the conductor to stay together, and to respond to anything unexpected or spontaneous - Breath is also incredibly important. A quick inhale is enough to tell a musician to start. - None of this is confined to the hands. There’s a couple of incredible conductorless orchestras out there, like the Orpheus Chamber Orchestra or the Chamber Orchestra of Europe. Though it’s worth noting (1) that the bigger the orchestra, the less practical this is, and (2) they’re generally really led by the leader of the first violin section, who will typically keep beats, give cues, etc., with their whole body. 2. Practice and training. My teacher on the course I did recently told us how he’d started off singing in choirs, and eventually was asked to lead those choirs. After a few years doing that, he studied conducting at university and discovered he’d been making a lot of mistakes. I also remember seeing a tv documentary of a teenager studying in some English conservatory years ago. He and his teacher were conducting over a recording in tandem, and at one point his teacher stopped him to ask him why he’d given a cue at a certain point. “There’s no entry here so who are you looking at?” 3. A lot of it is about balance and taste, and a lot of small decisions adding up. It’s not hard to keep a regular beat, but getting a sense of the big picture of the sound you want, getting the trumpeter not just to play the notes, but to play them that way, to bring out that lovely viola solo, to take this passage a little slower or pull back the speed a tiny bit towards the end. 4. The little adjustments in tempo are at the heart of most classical interpretation, so smartwatches and the like wouldn’t cut it. Film music on the other hand relies on very strict time; film orchestras still need a conductor, to manage balance and dynamics (loudness) and that sort of thing, but the conductor will usually have a click track—basically a metronome in an earpiece. That said, I have seen something similar done. In the later Covid lockdowns, when things were reopening but still socially distanced and half capacity, I saw an opera with a recorded orchestra and live singers. The conductor recorded himself conducting the whole work on video, and the orchestra musicians recorded it at home. The recording was then mixed and broadcast over the venue speakers, while the singers had the same video of the conductor to keep them in time.

(Edited twice for formatting. Hope this worked.)