Even seasoned aficionados of avant-garde music are unlikely to have witnessed a musician playing a mini concerto for bubble wrap. But that’s what the composer Tonia Ko is playing tonight. She’s at the front of the stage, miked up, rhythmically rubbing and rustling various sizes of plastic packaging while the string section of the London Symphony Orchestra play a suitably squeaky and discordant accompaniment. During a rubato-heavy “solo”, where she crunches some small-gauge bubble wrap and then “pops” a particularly large variety of industrial packaging, she even elicits applause.

This kind of thing is par for the course with Nonclassical, a series of sporadic club nights launched in 2004 by Gabriel Prokofiev. The grandson of the Russian composer Sergei and a fascinating orchestral composer in his own right, Gabriel also played punk-funk with the band Spektrum, made electronica under the pseudonym Medasyn and provided grimy production for the rapper Lady Sovereign, and he wanted to bring some of that demotic energy to the “contemporary classical” world, taking it out of the conservatoire and the concert hall. His Nonclassical sessions took place in unprepossessing pubs such as the Shacklewell Arms in Dalston or the Macbeth in Hoxton, where you’d nurse a pint of Guinness while string quartets played computer game music or Guildhall students made space-age sonatas on theremins.

Tonight Nonclassical celebrates its 20th birthday with an uncharacteristically huge showcase in front of around 1,500, playing small-scale pieces that have been performed at its club nights over the years, but arranging them for the LSO, under conductor Darren Bloom (who expands his own small-scale 2015 composition Xativa Street). Sasha Scott plays her synth-drum-driven piece Inertia, this time with a full orchestra mirroring her woozy, pitch-bending synth manipulation. Emily Abdy screams out the lyrics to Not Getting Any while her minimal backing takes on an epic, stompy, symphonic arrangement. A Christian Mason piece, based on a Tuvan folk song, sounds like Aaron Copland meets New Order. The centrepiece is the premiere of Sift, the first piece for orchestra by the electronic musician Beatrice Dillon; it’s a wondrously fractured, spiky, space-filled piece made up of interlocking fragments of atonality shared among different parts of the orchestra.

The highlight of the evening, however, is the Concerto for Drum Machine and Orchestra, first performed at the Village Underground in 2018, where various composers created ways of using the distinctive R&B sounds from a Roland TR-808 alongside an orchestra: best of all might be Josephine Stephenson’s final section, where the drumbox’s rolling tom-tom riffs and bleepy claves are set against drowsy, legato strings.

Part of Nonclassical’s ethos has been to remove the distinctions between high and low art, but there’s an irony that this big-budget celebration only emphasises notions of privilege, as orchestras are incredibly expensive, hierarchical institutions. Sometimes, small-scale laptop experiments really are dignified by being performed by 40-piece ensembles, and it’s wonderful that the eccentrics at Nonclassical are able to make that happen.