In my undergraduate degree at Peabody some of my classmates used to practice viola in front of their TVs. This always struck me as strange. How could they concentrate on their playing? They could only use part of their mind-the part that knows the fingering so well it can go on autopilot. This sort of autopilot playing is not uncommon in performance as well. The mind of the performer is either thinking of other things (what is for lunch?) or running a check list of "dos" and "don'ts". (Here comes the shift, remember to relax upper arm, don't land high, speed up bow).
Most of the classical music world recognizes that there is a serious problem with getting audiences to be enthused by this fantastic music. There is a subtle underlying belief that most of the public is not educated in this high art and can't appreciate it's nuances. I think, however, the issue is not with the music, nor with the public. It is with the modern performance practice.
Every good actor knows that in order to bring a character to life, they must, in part of their mind and heart, believe and live the essence of that character. They have to experience the struggles and joys of that character. Music performance should be the same. When Bach, Mozart, Beethoven composed, they were writing down expressions of their emotions and experiences. Now, that much time has passed, we have idolized the music by placing a glass frame around it, much as a Picasso in a museum. We play on stages lifted above our audiences, rarely make eye contact, often do not speak and try as hard as we can to pretend that we are in a removed realm such as through a screen or glass wall, separated from the audience. Our music has turned from expression to something removed and untouchable. We are more concerned about preserving the precise dynamic marking in the God, Beethoven's music than we are with internalizing and expressing the message.
Pop, Rock, Jazz, and other genres have this right. The performer is creating the song and presenting it to their audience as a form of their expression. They look at their audiences, relate to them, give personal stories, sometimes even walk into the audience. This leads to enthused audiences. Whereas with most classical music performances, the audience either attends your recitals to show support-like attending a child's ballet performance and cheering them on, or to observe and appreciate the high art in the concert hall museum. The older audience still culturally appreciates this, although they often doze and read the program notes, waiting for the movement to end. Millennials, however, are overall less impressed.
As a performer, we need to understand the expression of the piece, and then speak it to our audiences. Not aloof with our eyes closed, a spectacle, but as one would communicate any other form of expression. With the understanding that we are actually speaking with someone, our minds will be able to focus on the expression within the notes. Just as when we speak, the words we are saying is at the forefront of our thought-not the method for their execution. No one thinks, "I must now touch my tongue to the roof of my mouth and raise the pitch of this word". Much the same, with a musical performance, we must keep in our minds the expression as something relatable that we are communicating to our fellow humans who can understand and relate to these experiences, and may have something to say in return.