Historically speaking, it didn't pay to eat in live music venues. There may have been a legal requirement for the venue operator to supply food, but there was no requirement to make that food taste of anything more than a legal requirement.

Now we have Sydney's 45-year-old live music venue, The Basement, reborn as Mary's Underground. With $100 lobster and chips! And sommeliers! All that, ladies and gentlemen, and ... drumroll ... live music!

Mary's opened as a loud, good-times, trash-food bar in Newtown in 2013, and grew into a brand, now with three burger bars, a pizza joint and two pubs. They don't look too concerned, but for founders Jake Smyth and Kenny Graham, this must be their riskiest venture yet.

It's a delight to walk into the dark, dimly lit, split-level room and see a jazz trio plinking away on the Bugs Bunny stage, trays of cocktails in the long bar, and platters of oysters going out to tables from the Clam Bar at the back.

The menu is extravagant, laden with caviar and lobster, listing well-sourced produce such as saddleback pork and pasture-raised duck from Tathra Place in the Southern Tablelands. In spite of the same kitchen turning out burgers for Mary's upstairs, there's real cooking happening here from exec chef Jimmy Garside and head chef Joel Wootten, not just plonking-on-a-plate.

From the Clam Bar, raw scallops from the Abrolhos Islands in WA ($8 each) are simply served in the shell with a high tide of punchy macadamia ajo blanco and tiny dice of Christmas melon. An Underground (get it?) salad ($10) sees below-the-earth blue potato, kohlrabi and celeriac in a remoulade-like horseradish cream with a soft-yolked egg. Add lobster medallions for $10 – go on, I dare you.

Or go for broke with an EOFY lobster and golden duck fat chips ($100), the warm tail meat tossed with the sweet acidity of a bush tomato butter under a roof of gentle herbs. A leafy salad is pushy with vinegar; good-smelling bread rolls are tough on the teeth.

Best in show is the duck ($65/125), dry-aged in its Amsterdam red-light window for a week, brushed with red wine vinegar and maltose, spit-roasted and interleaved with fragrant, sweet/tart persimmon. A silky, sappy, biodynamic 2017 Hochkirch Pinot Noir ($85) does the honours from a wine list bristling with character.

It's a place of such whopping statements that it's a surprise when some dishes are just nice, enjoyable, pleasant. Like the pink, fat-fringed duck ham ($20) with pretty pickles; a big sweet-vegetabled wedge of tortilla ($35) topped with black truffle; or spit-roasted sugarloaf cabbage ($22) with almond milk dressing, chilli and fried nettles.

Then it's showtime again, with a spiky bombe Alaska ($18) of burnished meringue and luscious core of chocolate and mandarin drowned in a formidable pour-over of Del Maguey Vida mezcal and set alight.

And always, the music. It could be a tight, groovy jazz trio, a larger-than-life brass band or an Afro-Cuban six-piece, but it's determinedly foreground, refusing to be background. It's really what it's all about, although it does mean the food – expensive though it is – is relegated to the wings.

The bill isn't going to be pleasant, but you have to factor in that there's no cover charge, either – and what price supporting live music in Sydney and being able to eat at the same time?

The low-down

Vegetarian Two entrees, two main courses, five sides.

Drink Drinks director Caitlyn Rees lists minimal intervention wines, with a feature on Jurassic (from France's Jura), and maximalist cocktails.

Go-to dish Rotisserie Tathra Place duck, $65/$125

Pro tip Mary's mission is to support live music and musicians, so stop talking for a minute and listen.

Terry Durack is chief restaurant critic for The Sydney Morning Herald and senior reviewer for the Good Food Guide. This rating is based on the Good Food Guide scoring system.