I always remind my students that when we play we are always thinking about where we are, where we have been, and where we are going at the same time. In order to make for a meaningful performance, we have to be aware of where a phrase started and where it is heading. In order to make meaningful musical moments we need to set them up and release them. We need to be aware of the structure of the music we are playing, and we need to be hyper aware of what we happen to be doing at any given moment and where that action is taking us musically. Since no two turns around the fishbowl are identical, we strive to make the most out of the tiny nanoseconds of expressive difference, and, sometimes those little differences can make a world of difference in the way a piece "goes" in performance.
The air is electrified with the thrill of discovery. The beginning of each phrase becomes a "now," the duration of each phrase is an experience of "now," and the end of each phrase has a cadential (sometimes) sense of "now."
If we know the music well enough (and knowing something by memory doesn't always mean that we know the music beyond the notes, articulations, and dynamics), we can trust ourselves and be thrilled and entertained by whatever waves might come along, or whatever curve balls are thrown at us during the "now" of a performance. We can direct our awareness outward towards the people we are playing with, and follow their whims. We can enjoy the novelty and intimacy of the exchanges. And those intimate and novel exchanges are what we share with the people who are listening. We have an obligation to saturate the time with a meaningful sense of "now."
Perhaps it is because of that sense of "now" that I rarely listen to recordings more than once. A recorded performance is an image of something that was a "now," but a recording is always limited to what the microphone "hears" and/or what the camera "sees." I prefer to listen to recordings made in concert. A recording made in a studio, and submitted to scores of edits, does not offer me the same sense of "now" that a concert offers. A recording may be "perfect" (it certainly has to represent the intentions of the people playing and has to satisfy the people publishing it), and a concert may not be "perfect" (I distrust the idea of perfection in music), but the concert offers me and the other people in the room a meaningful "now." Lately I have been spending most of my musical time with live music: practicing myself, teaching students, rehearsing, playing with friends, or going to concerts.
In extra-musical life we enjoy the sense of now. My sense of smell during the particular "now" while I am writing this post is stimulated by the chicken stock I made last night reducing in the oven so that its flavor will become more concentrated. Come dinner time my sense of taste will be satisfied by those hours and hours of cooking time (not a "now" in itself, I guess, because it is a process), and dinner will be more meaningful because of the time spent letting the bones and vegetables cook. I have all day to anticipate it.
When someone plays a concert his or her weeks and months prior to the performance have been filled with figurative stock-making. That hour or hour and a half has been deemed "sacred" well ahead of time. Someone who performs a lot has a lot of "sacred" moments in his or her future, and someone who performs rarely has fewer, but they are just as sacred.
Our daily practice prepares us for whatever "now" happens to be in our immediate or distant future.