The cast of Lawrence High School’s “Showtime” rehearses April 13 in the school auditorium, 19th and Louisiana streets. “Showtime” is at 7:30 p.m. Thursday-Saturday at the school. Tickets are .

LHS senior Derrick Weishaar performs during a rehearsal for “Showtime,” which will have a mix of songs ranging from toddler-friendly fare to mature music by Kanye West.

LHS senior Evan Georgie tears through an air guitar solo during a rehearsal for “Showtime,” which opens Thursday at the school, 19th and Louisiana streets.

LHS senior Lucas Parker sings during a rehearsal for “Showtime.” The director is LHS teacher Cathy Crispino.

Rehearsals are under way in earnest at the auditorium of Lawrence High School for “Showtime,” the annual mashup of choral and pop music that’s become a community tradition. Forty teenagers crowd the stage and are giving their all for a rousing rendition of Queen’s “Somebody to Love.” Solo vocalists step forth and offer soaring renditions of their respective sections of the operatic ’70s rock hit, then step back to the choir behind and return to the wall of harmony. There’s dancing, air guitar solos and total commitment to the performance. In a final bit of stagecraft, as the song winds to a close, the choir leaves the stage and dances down the aisles of the theater.

It’s all very elaborate and looks exhausting. And then they have to go back and do it all over again. And then again. And then again. And so it goes for about an hour. Despite the grueling rehearsal repetition, the students still manage to summon up the gusto each and every time.

“Anyone can relate to finding somebody to love,” says LHS senior and “Showtime” performer Olivia Johnson of the Queen classic. “With such a big group of people, it’s so easy to feel the song and get into it. This is one of the easiest to really get into.”

Johnson is one of the nearly 150 juniors and seniors devoting their time and voice to “Showtime,” and she’s typical of the level of commitment to the venerable LHS production. “I suppose the big thing we’ll try to put in the show that we try to put in every year is a lot of energy,” says Addison Frei, another senior and “Showtime” member at LHS. “That’s really what it takes to make it successful. It’s a high-energy show.”

Students will try to sustain that energy for almost 30 pop, rock and hip hop songs. The playlist runs the gamut from toddler-friendly renditions of “You’re A Mean One, Mr. Grinch” to more mature and contemporary fare such as Kanye West’s “Love Lockdown.”

It’s a varied set that, perhaps most importantly, doesn’t overlap with Free State High’s own choral pop performance, “Encore.” Well, almost.

“Sure, there’s a little bit of friendly rivalry,” says the director of “Showtime” and the LHS choral department, Cathy Crispino. “We’re both doing the same Queen song … I’m sure they’re curious to see our treatment of it, which is a little bit different from theirs. It’s all in good fun.”

Adds Frei on the history between the two schools, “One thing I noticed from being able to see their show the past couple of years is, since it comes before ours, it’s very inspiring and motivating. We’ve got to at least be on par, so it inspires us to really work hard and rehearse.”

That back and forth seems to have bred a mutual respect. “The kids have a lot of friends at both schools and I think, especially in music, we really do support one another,” says Crispino. “I can tell you I went to opening night at ‘Encore,’ and there were tons of Lawrence High School kids there supporting and enjoying it. I know the same will be true here.”

It’s gotten to the point where the two shows have almost become a package deal in Lawrence, a sort of choral double header. “I think that ‘Showtime’ and ‘Encore’ are two treasures in this community,” Crispino says. “There are people who are long gone from having any other tie to the high school who come back every year for ‘Showtime.’ It’s a very big tradition. We fill the house for three nights and always have people calling ahead.”

It seems that this year will be no different, as “Showtime” has left a similar impression of the 2010 crop of performers. “It made my experience at Lawrence High,” Johnson says. “It was one of the things I really got involved in and could really bond with other people and meet a ton of new people. The process of auditioning and then making it, you meet so many people you didn’t know you went to school with. It was really important in my time at Lawrence High.”

While the music in this storied, nearly 40-year-old tradition is a lively celebration, there is an underlying note of bittersweet. “For us at Lawrence High School, ‘Showtime’ really marks the beginning of the end of the year,” says Crispino. “For me, it’s always very emotional watching these seniors. It will be sad to think about these kids leaving and going on. I’m happy for them, of course.”