It’s no wonder USC only holds one joint a cappella performance a year: Unleashing so much talent under one roof can be a little dangerous.

This year’s All Hail A Cappella concert, organized by USC a cappella group Reverse Osmosis and featuring other on-campus groups such as the Sirens, Trojan Men, Kosher Pig, SoCal Vocals and Troy Tones was a wild, explosive display of vocal talent — adjectives meant, of course, in the very best way.

Pitch-perfect · Reverse Osmosis, one of USC’s most popular co-ed a cappella groups, performs on stage in Bovard Auditorium at the annual joint a cappella concert Monday. Reverse Osmosis also produced the event. - Photo courtesy of Casey J. Dady

Such a vibrant and energetic celebration of the human voice has come to be expected from the yearly fall show, which allows USC’s six a cappella groups to show off their distinctive personalities and appeal to prospective members.

A long line of excited fans and a cappella enthusiasts formed outside Bovard Auditorium early Monday night in anticipation for the concert. The crowd was rewarded for its patience with 90 minutes of nonstop (excluding a short intermission) vocal acrobatics, entertaining choreography and spine-tingling harmonies.

The Sirens, USC’s only all-female a cappella group, opened the evening with none other than the queen of pop: Britney Spears. The ladies performed an energetic rendition of “Circus,” creatively blended with another Spears number, “If You Seek Amy.” The group also performed soulful versions of Tom Cochrane’s “Life is a Highway” and John Hiatt’s “Have a Little Faith in Me.”

In true yin-yang fashion, the Trojan Men, USC’s only male a cappella group, followed the Sirens. Always a crowd pleaser, the group was welcomed by an outburst of whooping and hollering from the audience (mostly high-pitched).

The screams escalated to dizzying decibels as the group performed its highly entertaining, brilliantly choreographed (crotch grabs and all) rendition of Michael Jackson’s “P.Y.T. (Pretty Young Thing).” The men then slowed things down with their second song and concert staple, Etta James’ “At Last,” after which they picked up the pace again with its fun, energetic set closer, “Vehicle” by The Ides of March.

Kosher Pig, the newest member to USC’s a cappella family, took the stage next in bubblegum-pink Converse sneakers and metallic ’80s gear. The group established its funky personality in choreographed performances of the Beach Boys’ “I Get Around” and Jason Mraz’s “You And I.” A humorous medley featuring songs such as Starland Vocal Band’s “Afternoon Delight” and T.I.’s “Live Your Life,” spiced up with a beatboxing solo by sophomore Gabe DaMast, closed the set.

A short intermission paved the way for the SoCal Vocals, USC’s oldest co-ed a cappella group. The group, dressed in black concert attire (with cardinal-and-gold ties for the men), started the second half of the night with a pulsating performance of Basement Jaxx’s “Good Luck,” featuring the impressive pipes of junior Rachel Saltzman. The SoCal Vocals also performed Peter Gabriel’s “Down to Earth” from Wall · E and the group’s iconic arrangement of USC’s alma mater.

After the SoCal Vocals, the men and women of Troy Tones — famous for its outrageous costumes — stumbled onto the stage feigning hangovers, clutching bottles of alcohol and wearing the stained remnants of “last night.” The act was almost believable — that is until they burst out in pitch-perfect harmony.

The group performed spot-on renditions of Cutting Crew’s “(I Just) Died In Your Arms Tonight” and Matchbox Twenty’s “Downfall,” but the highlight of its set was an adorable rendition of “Kiss the Girl” from The Little Mermaid.

Reverse Osmosis closed the jam-packed night with three flawless performances. The group’s soaring harmonies took Kansas’ “Carry On My Wayward Son” to a new level; its slowed-down version of Coldplay’s “Fix You” was pure and moving; and a schizophrenic-but-splendid pop medley featuring Rihanna, Backstreet Boys and Toni Braxton had audience members dancing in their seats.

All Hail A Cappella 2009 was an occasionally outrageous, constantly impressive showcase of student talent that could have only been improved with a few more songs (and, for loyal fans who have heard most of it before, a few more new songs). Overall, the concert served its purpose to a T, displaying the groups’ unique personalities, showcasing some major singing chops and inspiring singers in the audience to join USC’s a cappella family.

All six groups will be holding auditions Wednesday from 6:30-11 p.m. in Taper Hall. Auditions may vary slightly, but singers are advised to prepare a verse and chorus from a song of their choice.