Learn Spanish (Spain): El grupo canta en el concierto.

While the word banda exists, in Spain it is much more common to use el grupo (short for el grupo musical) when talking about a pop, rock, or indie band.

Since a band has multiple members, why is the verb canta (singular) instead of cantan (plural)?

Words like el grupo (the group) or la familia (the family) are collective nouns. Even though they refer to multiple people, the noun itself is singular. Because of this, it uses the singular él/ella/usted form of the verb (canta), not the ellos/ellas form.

I learned that en means "in" or "on". Why does it mean "at" in this sentence?

The Spanish preposition en is very flexible. Depending on the context, it covers the English words "in", "on", and "at". When you are talking about being present at a location or an event, like en el concierto, it translates naturally to "at".

Could this sentence also mean "The band is singing at the concert"?

Yes, it can! In Spanish, the simple present tense like canta can mean both a general fact ("sings") and an action happening right now ("is singing"). You don't always need a separate "-ing" verb form like you do in English.