It's hard to believe that a phenomenon three opera singers began has not only lasted for more than 15 years, but has spawned lots of imitators.

The trend began in the early 1990s, when Placido Domingo, Jose Carreras and Luciano Pavarotti launched The Three Tenors. The group has inspired many knockoff groups, perhaps most notably Three Irish Tenors and Three Mo' Tenors, the trio performing with the Indianapolis Symphony Orchestra through Sunday at Hilbert Circle Theatre.

The various spinoff groups have generally stuck with a mix of classical and popular music. Except for their individual voices, it is the pop music that most sets apart one group from another.

On Friday night, the pop element worked especially well for the black American singers in Three Mo' Tenors, whose huge spectrum runs from musical theater to spirituals to soul.

Several singers have performed as part of Three Mo' Tenors. This touring ensemble consists of the stylistically multi-talented James Berger and Duane A. Moody, both from Washington, D.C., and Robert Mack of Newark, N.J., who replaced the originally scheduled Victor Ryan Robertson. Joseph Joubert conducts the ISO.

This weekend's program features a full orchestra and rhythm section. Vocalists bounce from trios to solos and duets, all fully choreographed.

The show opens with Italian and French opera arias including "La Donna e Mobile" from "Rigoletto" and "Pourquoi me Reveiller" from "Werther." It moves on to adaptations of "Bring Him Home" from the grand-scale musical "Les Miserables" and songs from the revue "Five Guys Named Moe."

Second-half highlights included a cheesey pop medley with "Love Train" and "Midnight Train to Georgia," and a poignant Ray Charles homage featuring an upbeat "Hit the Road Jack" and a laidback "Georgia On My Mind." A smart spiritual setting blended "Lord How Come Me Here" with "Hush, Somebody's Calling My Name."