I am a singer in a performing group. Our group is invited to perform at an noncommercial cultural event this summer at Chicago by a U.S. organization. 

We were told that we need to apply for P3 visa to come to U.S. to participate the event. What kind of documents we need to prepare the P3 visa application?

The P3 visa is for artists or entertainers who come to United States to develop, interpret, represent, teach, or coach in a program that is considered culturally unique, either individually or as part of a group. The art or entertainment program may be of either a commercial or noncommercial nature. 

The P3 applicant must be coming to United States to participate a cultural event or events that will further the understanding or development of an art form. For P3 visa application, the U.S. employer should submit an application to USCIS on behalf of the alien applicant, including the following evidence:

1) statements from experts in the field, to show the authenticity of the person or group’s skills in performing, presenting, coaching, or teaching the unique or traditional art form.