It may be just my own approach (although I am somewhat experienced in these matters) but for me there is only one technique in making any performance smooth and polished.
I’m not talking about the musicians: there are countless people extolling the value of practise, talent, luck, alcohol etc. I’m talking about the performance as a whole. We’ve all got stories of concerts which were bad, not due to a deficit in performance skill, but in execution of a successful event. Mine involves Notre Dame cathedral, 2 degree temperatures, no toilets, and a concert starting 45 minutes late. The music was amazing, the concert was not.
I’m also talking about classical music. In theatre and musicals they keep on trying until they get the performance they want (try seeing a first preview and then a press night and prepare for some surprises) showing that the smooth performance is a product of elimination and trial and error.
In classical music (concerts, recitals, opera, anything) you only really get one shot at success, and so getting it right (or not) becomes a matter of prediction and experience.
For me, the ‘trick’ is to imagine your performance going perfectly: what does that look like, how does it run. Then, you do two things – take it apart (what did it need, what was used, what did it feel like in the room) and work out how to get those things into that room at exactly that time. Then it’s just working backwards from there to get it done.
Easy, right? But just thinking about the end product gives you the steps you need to achieve it. We work in a standardised industry, meaning we can visualise the final concert without too much effort. This can apply to performers too: work out what the performance needs to be, plan on how to get there, hope you have the skills to do so (we have the luxury of outsourcing and freelancers).
Of course this ‘simple trick’ (I’m moving into clickbait) assumes no spanners are thrown in the works: no-one changes repertoire, no-one gets sick, the soloists visa comes through, the venue doesn’t flood and the piano doesn’t disintegrate. Of course, those of us with the special training know how to handle these, but I swore an oath not to tell you. But I definitely know. Yes.