“Loose lips sink ships.”

That World War II adage appeared on posters in an advertising campaign to warn soldiers and citizens to avoid conversations that could imperil the war effort. The phrase entered the lexicon to impugn those who indulge in careless talk.

Looked at another way, with the advent of the talking motion picture, loose lips could sink a motion picture. “When the lips move, the words come out” is a byword for “the talkies.” Voice and lips must be in synchronization, aka in sync. That’s one thing. What if the lips of the actress or actor elicit a voice that is harshly-accented, grating (equivalent of the contemporary vocal fry) or shrill?

This dilemma is at the heart of the premise for “Singin’ In The Rain,” the musical theater adaptation of the classic 1952 Hollywood movie musical (starring Gene Kelly, Donald O’Connor and Debbie Reynolds) on stage at The Pennsylvania Playhouse, Bethlehem.

The term in sync can also refer to persons, groups or events that are in time, in tune or in harmony. The Pennsylvania Playhouse production of “Singin’ In The Rain” is in sync with a fun show that brings to the stage a fascinating and entertaining story set in 1927 when “The Jazz Singer,” the first feature-length movie with synchronized recorded music and lip-synchronous singing and speech, was released.

The 6 p.m. June 1 performance was seen for this review.

In the Playhouse show, Don Lockwood (Salem Perez Torres) and Lina Lamont (Zoe Mulzet) bask in the red carpet glow at the premiere of their latest silent film, “The Royal Rascal,” directed by Roscoe Dexter (Thomas McElhinny) as they are interviewed by Dora Bailey (Melissa Dorflinger), a Hollywood gossip columnist.

The movie’s producer R.F. Simpson (Charlie Dalrymple) decides to revamp the next Don Lockwood-Lina Lamont starrer, “The Dueling Cavalier,” into a talking picture. The preview screening is a disaster because of Lamont’s out-of-sync and screeching voice.

Lockwood’s sidekick Cosmo Brown (Joey Troiano) backs the idea of turning “The Dueling Cavalier” into a musical, “The Dancing Cavalier,” with aspiring actress Kathy Selden (Lucy Moore) dubbing the dialogue and singing for Lina Lamont.

The movie and the musical has book by Betty Comden and Adolph Green and lyrics by Arthur Freed and music by Nacio Herb Brown.

The Pennsylvania Playhouse production, directed by Rachel Lutz with assistant director Corrine Philbin, music director Amanda Haag and choreographer Jess Sturm, has a number of knock-out production numbers, with a great supporting cast and terrific singing and toe-tapping ensemble, especially in the finale.

The female Flapper Era costumes are beautiful. Costume designer is Todd Burkel with co-costume designer Nate Kuhns.

Set and Lighting designer is Brett Oliveira.

The black and white videography Braden Drake, replicating the silent films is impressive and convincing.

Salem Perez Torres (Don Lockwood) portrays an undeniable sincerity and is in fine voice for the lovely songs “You Stepped Out Of A Dream” and “You Were Meant For Me” and the show’s title song, “Singin’ In The Rain.”

Joey Troiano creates hilarious antics as Cosmo Brown in the novelty tunes “Make ‘Em Laugh” and, with Torres, for “Moses.”

Andrew Maldonado (Production Singer) has a bravura turn singing, “Beautiful Girls.”

Lucy Moore (Kathy Selden) is in strong voice for “You Are My Lucky Star” and “Would You.”

Torres, Moore and Troiano combine for an irresistibly cheerful “Good Morning.”

One of the funniest scenes is when the ruse is revealed as Zoe Mulzet (Lina Lamont) lip-syncs at a microphone while Lucy Moore (Kathy Selden) sings from behind a stage curtain. Mulzet renders this difficult-to-pull-off scene perfectly.

Zoe Mulzet gets the show’s biggest laughs whenever she’s on stage. At the same time, she’s sympathetic in her characterization, especially during her lament, “What’s Wrong With Me.”

“Singin’ In The Rain,” from its Roaring 20s’ story origins to the hit Hollywood movie emblematic of post World II era optimism to the mid-1980s Broadway musical reimagining, speaks to a particular American philosophy of overcoming obstacles with love and pluck.

The Pennsylvania Playhouse production, as the title song goes, will put a smile on your face. Who couldn’t use some sunshine in this time and place?

“Singin’ In The Rain,” 7:30 p.m. May 30, 31, June 6, 7, 13, 14; 6 p.m. June 1, 8, 15, Pennsylvania Playhouse, 390 Illick’s Mill Road, Bethlehem. 610-865-6665, http://www.paplayhouse.org/