In its fourth year, Richmond Rhythm — the annual gathering of Virginia collegiate a cappella groups — is going “American Idol” on us. But don’t worry: Superfluous television fluff won’t be found in this friendly competition of throats, held by the ever-expanding Virginia Commonwealth University vocal group, Ramifications. Audience members will judge seven groups representing five of the state’s universities to determine who has the best collective pipes. Opening the festivities will be North Carolinian a cappella group Twisted Measure, from Elon University. Richmond Rhythm takes place Friday, Oct. 11, at the W.E. Singleton Center for the Performing Arts. Doors open at 6 p.m. Tickets are $20 ($10 for VCU students and children younger than 12 are free). richmondrhythm.com.