This issue has a few aspects.
1. First of all, the music played in the concert must not be among the ones that are religiously regarded as haram. Otherwise, it is not permissible to go to such a concert. Besides, it is not permissible for a man to listen to a woman singer.
2. The woman must wear clothes in compliance with tasattur/hijab.
3. A non-mahram woman and a non-mahram man must not sit so close to each other as to touch each other.
In fact, it is necessary to avoid doubtful things. It is necessary to be careful in this age, when mischief is widespread. We think it will be useful to prefer harmless ways. When the concerts of today are considered, it is clearly not possible to say, "There is no drawback to going to concerts."