Minstrel Magic
Considering how flashy those bards are, their magic is surprisingly subtle.
Though considered the weakest of the magic types, minstrel magic still has its uses. While the students of the Academy of the Arcane learn to harness the elements and the students from the Circle of Mynelion know the art of healing, the bards from the Minstrel's University can nudge emotions, disappear only to reappear into another place, or appear hidden from view altogether.
Schools of Minstrel Magic
There are three recognized schools of minstrel magic: Beguiling, Illusion, and Discretion. Not much is known about either of these as the bards keep their secret ways hidden from the uninitiated. However, since the bards have been around for a while now, people have noticed bits and pieces of their abilites.
Perhaps the most well-known of the three schools, Beguiling is the art of carefully nudging people's emotions in some way. The most used way is to make inspiring speeches a bit more inspiring, but they have to use it for more than that, right?
Some people say they have seen bards flicker out of existence only to reappear a few feet away from their original location to get out of the way of their enemy's weapons.
I don't know about you, but I'm sure I saw a bard in this room a while ago, but there's no way to leave the room without opening a door so he should still be in here. Now, where did he go?
Tricks
The specific effects that are taught to bards are called tricks. While individual bards can use their magic in other ways than as explained in these tricks after experimenting, most bards only know a few tricks and are happy with this.
This is what most Bards in D&D and similar campaigns lack. The understanding that Bards are uniquely qualified to set the emotional tone of everything that happens with the party. Love how it's a separate school of magic here ;)