When the conductor Christopher Warren-Green picked up his baton to begin a concert in London’s Cadogan Hall last Wednesday, it was for a night of music that had been hanging in the balance.

Ahead of the earlier rehearsal with the London Chamber Orchestra (LCO), some of the musicians had pulled out in protest at the way they had been treated over the past five months, during which time none of them had been paid.

“It is a real battle working as a professional musician in this city now,” one LCO musician told the Observer. “We are not paid much and so have to do other jobs, while also keeping up our hours of playing. So we certainly need to be paid when we do work.”

There was a scramble to find enough musicians to enable the concert in the 953-seat Chelsea venue to go ahead. The managing director of the orchestra, Jocelyn Lightfoot, has since told the Observer that overdue payments were made last week.

The trouble, she said, stemmed from a decision by Barclays Bank to freeze the orchestra’s account – a problem that has also seriously affected the finances of charities and other cultural and religious groups, including the classical music venue, St John’s Smith Square. Under the bank’s obligation to help prevent financial crime it had requested further information from some customers in order to keep their accounts active.

Efforts to reopen the account, frozen by Barclays “with no prior warning”, said Lightfoot, took four months. “We kept the musicians informed during this period that their payment would go out as soon as the account was reopened, but as the timeline of the reopening was further delayed many times, it was difficult to provide musicians with a clear timeframe,” she said. Musicians have also been asked to come forward with any outstanding invoices.

“We understand the monumental strain on this body of freelancers whose opportunities to work have been reduced and jeopardised due to sweeping cuts to orchestral funding,” said Lightfoot this weekend.

“Many of these musicians have had their work curtailed due to Brexit and they are still suffering the aftermath effects of the pandemic. There is great cause for concern for these highly skilled, immensely talented players whose role and value in society is under-appreciated.”

LCO musicians do other work, not always musical, as the orchestra mounts only a few concerts each season. The management deems each concert and its rehearsal to be equivalent to two days’ work. The musicians also work with the Music Junction education programme to promote “leadership, community and inclusion by providing opportunities for children”.

The chamber orchestra, founded in 1921, is about half the size of a full-scale symphony orchestra but it boasts experienced leadership in the form of long-term music director Warren-Green, also an accomplished violinist who conducted and arranged the orchestra for the wedding of the king and queen in 2005. The president of the orchestra is internationally renowned pianist Vladimir Ashkenazy.

The account shutdowns threatened the work of the Surrey-based Clockwork charitable trust and the Ogmore Valley Male Voice Choir, among others. A Barclays Bank spokesperson said: “We take the protection of our customers’ funds and data extremely seriously.

“As part of our ongoing responsibility to help prevent financial crime and to meet our regulatory responsibilities, we are required to ensure we hold up-to-date information regarding our customers’ accounts. Customers are also required to inform the bank in a timely manner of any change to their legal status relating to their business, charity or trust.”

The LCO, which two years ago dropped the requirement for formal dress for its musicians so that they could express their “individual personalities and backgrounds”, is committed to “breaking down barriers to orchestral music and making a positive impact on the community”.

It has also made a commitment to play new music in an environment that veteran music critic Norman Lebrecht says has “dried up”. London, he recently argued, “is falling off the music map”. The LCO concert last week included classical hits from Mozart and Sibelius. It also premiered a horn concerto by Gavin Higgins.

• This article was amended on 16 February 2024. An earlier version said “half of the musicians walked out [of their rehearsal]” on the eve of a concert at the Cadogan Hall in protest over unpaid fees. In fact, some musicians had withdrawn before the rehearsal and had to be hurriedly replaced, but none walked out of the rehearsal itself. Amendments have been made to the headline and opening text to reflect this.