Thousands of primary and secondary schools are suffering from lack of cash - on average they have just pounds 340 a year to spend on musical instruments.
The figures are part of a study commissioned by the Co-op, which has launched a Music for Schools Initiative with the backing of the classical percussionist Evelyn Glennie and the rock superstar Phil Collins.
The study showed that:
n Four in five schools (82 per cent) do not have enough musical instruments to go round
n Two-thirds (63 per cent) blame poor funding for the shortages
n Three in five schools (59 per cent) say pupils have been denied the chance to learn an instrument.
The Co-op, whose scheme begins today, is giving away vouchers for free musical instruments to shoppers who spend pounds 10 at participating stores.
Ms Glennie said: "Music often seems to be the soft target for the hatchet man looking to cut school budgets . . . New research overseas has shown that learning music can help children improve in other areas, such as reading - so it's a shame so many of our youngsters are losing out."
Phil Collins added: "Most kids want to learn to play musical instruments - but it seems the demand often exceeds the availability of instruments in schools."