The word concierto word translates into concert. This is a singular noun used to point out a live music being performed in front of an audience.
2. grupo
The word grupo translates into music group. This is a singular noun given in masculine form and is a group of musicians who perform instrumental or vocal music.
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Therefore, the dialog is as follows:
<em>Guillermo: </em>No puedo creer que vayamos al concierto de clandestinos. Es mi grupo favorito.
Whose translation is:
<em>I can't believe we are going to the</em><em> concert</em><em> of clandestinos. It's my favorite </em><em>music group.</em>