The musicians are often far away, on an elevated stage.
Your ticket tells you which seat you’re allowed to take. Which stranger will be sitting next to you during the following hour.
Since about a hundred years ago, a concert of classical music has been a solitary experience.
In smaller halls the atmosphere is less rigid.
For instance, you are allowed to pick your own seat.
On occasion the musicians may even give a cheerful introductory talk. This momentarily provides for a pleasant atmosphere. Often there are even little jokes.