Nico Muhly describes A Scream and an Outrage, the weekend of events he curated at the Barbican this weekend, as like a dinner party, “a gathering of friends and family new and old; loosely organised”. A wonderfully relaxed vibe was even present on entering the hall for the first concert on Friday: Muhly and a few pals were sat at the side of the stage, quietly and tastefully improvising around a drone. The sense of conviviality which ran throughout the evening was an unusual and welcome thing for a (basically) classical concert. The music, on the other hand, was very uneven.

First, the good. David Lang’s percussion concerto man made was given its world première in the first half, and it sounded like a real keeper. Written for the excellent New York-based quartet So Percussion and performed with the BBC Symphony Orchestra under Jayce Ogren, man made has the four soloists cycle through a progressively more artificial series of instruments, starting with twigs and ending with various tuned percussion instruments and a drum kit.

Watching these four virtuosic percussionists snap small twigs in neat rhythms with each other was an astonishing, engrossing beginning. Moving through a hypnotic section for tuned wine bottles, in which the soloists all played the same meandering, trippy chromatic riffs, later stages also involved four aggressively thwacked dustbins. The orchestral players were background figures for most of this, though they did (quite deliberately) overpower the soloists at times – but their material was audibly derived from the percussionists’, and the quizzical, never-quite-stable stab chords they played formed an intriguing backdrop to it all. As so often with Lang, this was an uncannily insightful piece – here, alongside the musical element, he was clearly exploring some thoughts about technology – and I could easily have listened to twice as much of it. I guess it won’t be an easy piece to tour, with all its many props, but it would be worth the effort.

Second, Paola Prestini’s “multimedia cantata” Oceanic Verses, whose European première comprised the second half. This piece told a very unclear story to do with the south of Italy, with a Scholar (Helga Davis), a Peasant and a Soldier who fall in love (Hila Plitmann and Chris Burchett), and a Sailor (folk singer and accordionist Claudio Prima). In addition to displaying the sung text, surtitles were also used to give information about the plot which otherwise would have been totally absent – I wondered whether this information couldn’t more efficiently have been integrated into the projected film (by Ali Hossani), but the visuals instead were made up of glamorous but essentially unhelpful shots mostly depicting the south-Italian scenery, in a slightly annoying Instagram-esque style.

Neither the music nor the text helped matters; both, in fact, felt clichéd. There were a number of what were presumably traditional south-Italian folk songs integrated into the score, but while it all sounded quite lush, it also sounded very familiar and safe, unwilling to do anything beyond telling the story – as already mentioned, though, there wasn’t much of a story to tell. The libretto (Donna di Novelli) was not convincing, sometimes too bland (Sailor: “Do not enter. You do not belong.” Scholar: “I will enter”), sometimes trying too hard (“The Mediterranean Sea is an immigrant itself”). The low point was a descriptive surtitle which read: “In a field, the Soldier finds the Scholar researching”, which suggests a bafflingly literal conception of what “field research” actually involves.

The singers were a varied group: Helga Davis was billed as a “folk improviser”, and had a part sometimes traditionally classical and sometimes far more free. On one occasion her music slipped into an incongruous heavy blues style. She gave a commendable performance throughout. So did Hila Plitmann and Christopher Burchett, Plitmann sounding especially agile in some taxing high passages, and I enjoyed Claudio Prima’s contributions too, only wishing there had been more accordion. Ogren conducted eloquently, the BBC SO played very well, and the BBC Singers were underused but as excellent as ever.

The Singers had also delivered a fine rendition of Nico Muhly’s new choral piece, which opened the evening: An Outrage was a pleasant setting of a sacred text, in the composer’s increasingly familiar, light, melodic style. It all took place above the drone which Muhly and his friends had been playing on our arrival in the hall, and the effect was calming and gentle. This was an enjoyable piece, though not by any means an outrageous one.