Towcester Studio Band had a quarter of its instruments stolen when burglars broke into the band's clubhouse in Bransons Lane, Towcester.
Members of the band, which was founded in 1910 and is rated in the world's top 200, fear their prized intruments will be melted down for cash.
Chairman bandmaster, Phillip Bearman, said he and some colleagues were going for a coffee on Thursday evening when they noticed an instrument case down an alley.
He said: "They must have taken the instruments but left the cases which makes it even more likely they were taken for scrap. In some ways it was a godsend because they could have taken much more.
"We had some old radiators taken from outside the building recently. Builders working nearby noticed men loading them into a van. We were going to throw them away anyway but we think they were also taken for their scrap value."
Instruments stolen were a Soprano cornet, a Flat cornet, a tenor horn, two Flat euphoniums, a brass trombone, drums and cymbals. Bottles of wine were also taken.
Police have said the break-in took place overnight between Wednesday, June 6 and Thursday, June 7, but band members believe the crime may have happened later.
Mr Bearman said: "We think it may have been Thursday afternoon because one of our group called in at the band hall and noticed that some things were out of place but they didn't think anything of it. The burglars may have been disturbed and waited until the coast was clear before carrying on.
"The result is that 25 per cent of our musicians have no instruments to play. This will put us back a lot because we have various jobs lined up in the next few weeks. But some other local bands have offered to lend us some of their instruments to help us out."
It is the latest in a long line of thefts following a rise in the value of scrap metal. Opportunist thieves have raided churches and building for roof leading while several business have also been targeted.
Anyone with any information can contact police on 08453 700700 or Crimestoppers, anonymously, on 0800 555111.
nicola.shaw@northantsnews.co.uk