This verb is used exclusively for the case where there is a spontaneous and numerous public meeting, such as for a claim or a celebration. Usually a march, a picket, a popular demonstration are called by an organization or through a mass media that encourages them, but when it arises motu proprio it is said that it is self-convened, and it is in these cases where the verb 'self-summon' appears, which unites self-and-call.
