GIRL CRAZY

At the Mainstage, 14th Street Y, 344 E. 14 St. Through Sept. 16. Call (212) 362-0713.

CONCERT revivals of old musicals come in all shapes and sizes. There’s Encores!, which presents old gems elegantly, with star performers, a full orchestra and a shortened book.

And then there’s Musicals Tonight, with unknown performers, a single piano and the complete, unaltered original book. Take “Girl Crazy,” the 1930 musical for which George Gershwin wrote the music, his brother Ira the lyrics, and, alas, Guy Bolton and Jack McGowan the book.

When “Girl Crazy” was put on Broadway a decade ago as “Crazy for You,” it was revamped and rethought and rewritten. When you see “Girl Crazy” at Musicals Tonight, you’ll know why.

The plot is quaint and creaky, character stereotypes abound and political incorrectness reigns. To wit: Gieber Goldfarb is a New York cab driver who winds up running timorously for sheriff in Custerville, Ariz., disguising himself as a “sue” Indian; one gal is a San Francisco hooker, and the cowboy chorus boasts of its aim to “shoot the fairies.” The main story itself – about a New York playboy straightening himself out in Arizona – is a bore.

What “Girl Crazy” does have is amazing songs, and they’re done here with vocal charm, albeit with pianistic charmlessness.

Cowboys croon “Bidin’ My Time”; the romantic leads – Perry Laylon Ojeda and Kelli Rabke, both with melodious, subtle voices – do “Embraceable You”; the Frisco gal, nicely sung by Rachel Hale, belts “I Got Rhythm.” (In case you were wondering, the stars of the original were the as-yet-unknown Ginger Rogers as the nice girl and Ethel Merman as the Frisco gal. Wow!)

As the cowardly sheriff, Michael Lluberes has fun with “But Not for Me” – imitating Chevalier and Jolson – and also with “You’ve Got What Gets Me,” which he sings with fellow comedian Rebecca Rich. Such songs are Gershwin masterpieces, and their superiority to their settings in “Girl Crazy” is striking. Under music director James Stenborg, the chorus brings off such stunts as carrying the melody by clicking their tongues.

“Girl Crazy” is historically curious and musically enchanting. Too bad one has to sit through such a tedious book.