by Peter Debruge

Fake hair and trick shots simply can’t transform Ethan Hawke into short, balding musical legend Lorenz Hart — which is too bad, since it distracts from a wonderfully written movie.

Witticist-lyricist Lorenz Hart would cringe at the pun, but “Blue Moon” is nothing if not a funny valentine to the tortured (closeted, Jewish, alcoholic, diminutive) songwriter who died in 1943 at age 48, having drunk too much on opening night of his final collaboration with composer Richard Rodgers. Set six months earlier, Richard Linklater’s splendid portrait stars a courageous but egregiously miscast Ethan Hawke, chewing the scenery from a one-foot trench in the floor. Like a backstage pass for Broadway buffs, it’s one hell of a show for those in the know and a sparkling introduction for the uninitiated.

This was not a happy period in Hart’s life, and though he comes off charming and clever — the showman-cum-show queen — what makes him such a deserving subject are the layers of insecurity and self-loathing for which his patter is so clearly overcompensating. “He was the saddest man I ever knew,” the singer Mabel Merced once said, a quotation that sets the stage for an ever-so-theatrical hour and a half.

Confined almost entirely to a single location, “Blue Moon” unspools at Sardi’s, the legendary midtown New York restaurant, immediately following the opening of “Oklahoma!” For Hart, showing up (without a love of his own) must have felt like attending the wedding of the woman he dated for two dozen years, and with whom he’d conceived at least as many kids. The date is March 31, 1943, and there’s a war on, although it’s a cold one between the former songwriting duo.

Rodgers (Andrew Scott) had broken off his creative partnership with Hart earlier that decade, choosing to team up with Oscar Hammerstein (Simon Delaney) instead on “Oklahoma!” which would prove to be a far bigger hit than anything he and Hart had written — if you like that sort of thing. (Personally, I’ve always found “Oklahoma!” to be a corny, borderline-unbearable show, so it’s great fun to see the envious Hart cut it down to size.)

Showing up at Sardi’s before the “Oklahoma!” crew arrive, Hart makes his way to the bar and swears not to drink. As if to anticipate any “Casablanca” comparisons, Hart starts picking apart the Humphrey Bogart movie in front of Eddie the bartender (Bobby Cannavale), but for all his smooth talk, he’s not fooling anyone: Hart will be drunk before the end of a night that, like the beloved Warner Bros. classic, acknowledges that the best years of their relationship have passed. (They’ll always have “Pal Joey.”)

During their prime, Rodgers and Hart helped carry musical theater into the modern era, writing songs that moved the plot forward and sounded, at least when compared with what had come before, more like the way people spoke. While waiting for Rodgers (Andrew Scott) to show up, regales Eddie and the few other people in the room about his latest infatuation, a young woman named Elizabeth Weiland (Margaret Qualley), whose real-life correspondence with Hart inspired Robert Kaplow’s urbane and endlessly quotable screenplay for “Blue Moon.” Although it’s now widely accepted that Hart was gay, the movie offers a more interesting interpretation: “To be a writer, you have to be omnisexual,” he quips.

Hawke clearly relishes the reams of great dialogue he gets to deliver here, but I can’t begin to imagine why he or Linklater (who’ve collaborated on eight of the indie director’s features before) thought the Texas-born bohemian was right for the role of a short, balding, gay Jew from Harlem. Hawke is none of those things, and though he gives a magnetic and often moving performance, the various tactics used to pass him off as what Rodgers called “the shrimp” prove distracting, from having him stand a foot below his co-stars to slapping a comb-over bald cap on top of his hair.

It’s like casting Matthew McConaughey as Truman Capote. Instead of watching the actor’s facial expressions, I found myself staring at the way Hawke’s forehead made V-like creases at the base of his widow’s peak, unconvincing covered by a Mel Brooksian wig. It’s a problem even before the star takes off his hat, and remains the elephant in the room for the rest of the movie.

Along similar lines, as a straight man, Linklater recognizes the sexual tension in scenes between Qualley and Hart, but looks right past the homoerotic moments baked into the script — like the one where Hart follows “Knuckles” (Jonah Lees), the fresh-faced pianist in the neatly pressed uniform, to the men’s room. The director’s second feature with “Me and Orson Welles” screenwriter Kaplow makes a poetic bookend to that project, which transported us to the early days of a towering American talent (wisely casting a virtual unknown as Welles).

Here, we find ourselves at the other end of a creative career, watching a brilliant but ultimately pathetic man try to pitch his former partner on a new collaboration, even as Rodgers reveals why they went their separate ways. His own harshest critic, Hart intuitively recognizes the strengths and shortcomings in everyone else’s work, from Gershwin to “Oklahoma!” Beware any show that sneaks an exclamation point into its title, he warns, chiding Rodgers for “pandering” to audiences with sentimental romance. He aspires to more emotionally complicated work, which “Blue Moon” certainly is — the movie at least, the song not so much.

Kaplow crams his script with trivia (including the reason “Blue Moon” makes Hart cringe) and inside nods, some easier to recognize than others. He places essayist E.B. White that night at Sardi’s, suggesting a “Picasso at the Lapin Agile”-like effect, where Hart gives him the idea for “Stuart Little.” And in the same scene where Hammerstein thanks Hart for paving the way, he introduces a precocious young Broadway savant named “Stevie” (Cillian Sullivan), who has the nerve to call Hart’s work “sloppy” to his face (a conclusion drawn from Sondheim’s “Finishing the Hat”).

By this point in the film, I’d finally stopped staring at Hawke’s hairline and accepted him in the role, making peace with Linklater’s choice to let his Hart do the talking.