Celebrated American artist Julian Barker (Martin Bendel), a contemporary of Warhol and Bacon, is dying of pancreatic cancer. While Julian attempts gamely to continue painting, drinking and shagging until he drops dead, politicians, admirers and former lovers emerge from the woodwork to squabble over his legacy – both financial and emotional.

Each has a genuine claim over Julian, whether as a commodity, an inspiration, a benefactor, or simply as a friend. Which of these claims, the play asks, is most valid? To whom does a public figure’s legacy rightfully belong – to himself, to his public, or to his bereaved?

Julian is a largely offstage presence, cloistering himself in his studio and allowing his devotees to fight amongst themselves. Director Adam Spreadbury-Maher resists confrontational histrionics in favour of calculating nastiness, enabled by some delicious turns of phrase from playwright Daniel Reitz. Julian’s current and former lovers, Chad (James Holmes) and Marcus (David Price), have an especially honest and vicious enmity.

Beyond these enjoyably frank exchanges the play is heavy on flimsily motivated exposition. Backstory details are revealed in monologue to the subject, who presumably already knows his own life story, but sits through the lecture anyway for the audience’s benefit. Spreadbury-Maher’s directorial understatement allows the dialogue to shine when it’s good, but leaves the stage too static when exposition slows the pace.

Stylistically and thematically, Studies for a Portrait breaks no new ground, but it does attempt to sow something worthwhile there. Every play like this one is another step towards relocating non-heterosexual people from the LGBTQ Theatre bracket into the artistic mainstream. It isn’t an overt call to arms, but it’s one more raised fist in an invisible revolution.

Saturday Night by Zoë Simon is an honourable attempt to take on some very big questions about men and women, London, and the world. The play wants to draw connections between global and domestic violence, state-sponsored war and state-sponsored prostitution, but it doesn’t have the intellectual weight or knowledge of the world to bring off this massive narrative challenge. Too many of the characters feel completely unreal, and resort too easily to yelling, mauling the furniture, or mumbling the usual gloomy platitudes. And, as a conclusion, “it’s pretty grim out there” scarcely does justice to the piece’s heavyweight ambitions.

The cast of nine works hard to bring consistency, humanity and humour to an often bitty and occasionally ranty play. Jenni Maitland gives a good turn as aggressively post-feminist Annie, all attitude and assertiveness and defensive short-sightedness, wavering dangerously between knowingness and naiveté. Frank Doody, as her reality TV star boyfriend, delivers some nice lines with deadpan panache. And Debbie Korley is persuasively scary as a streetwise sex-worker, but never drops her guard or gives a hint of what she might have dreamed about before she became worldy-wise Lulu. As the innocent who gets led astray, Elizabeth Cadwallader is courageously gawky and asexual, and her sudden awakening to the reality of her new job is unexpected and shockingly straightforward.

Vicky Jones’ self-conscious, slow-footed production doesn’t do much to mask Saturday Night’s structural weaknesses. The show’s too long, and far too sluggish, and the inevitable pole dancing in the middle is pretty gratuitous. The song at the end is inexplicable and awful, and seriously knocks the play’s pretentions to moral seriousness, as a relentlessly earnest and high-minded ninety minutes descends to wallowing in sentimental slosh. But there are some promising performances here, and a commendable commitment to using theatre to try to talk about the big issues of our time.

The multi-talented company move between instruments with aplomb, and find a purpose and cohesion in their collective music that all too often eludes them elsewhere in the play. Joe Evans’s score skilfully reveals the troubles and dreams of the lonely souls who bring their woes to the piano.

Meanwhile the story jolts alarmingly between realism and allegory, with disconcerting shifts of tone and style that wrong-foot some of the cast into emoting and portending madly. The best moments are the most intimate, moments when these relentlessly self-dramatising characters stop posturing and start behaving like real people.

These passages of music and silence, late night ramblings and private jokes, are the most successful parts of the evening. Johanna Stanton makes more of a few speechless moments by the piano than she does of the rest of her lines put together. Nic Van Gelder is quietly impressive as her tongue-tied admirer, hiding his true feelings behind the keyboard. And Michael Chadwick is a low-key delight as a drunken, rueful clown, forlornly and hopefully trying to hold the show together.

Somewhere in all this, there’s a neat, touching, melancholy little musical, about shifting from the black notes to the white, and believing in the possibility of happy endings, despite experience. Rapunzel’s Last Midnight, as it stands, ain’t quite it. But sometimes that other show shines through an evening of too many words, too many tangled stories and too little faith in a truly evocative score.