The Educational Institute of Scotland (EIS) teaching union hit out despite the unveiling of a £1 million Scottish Government fund to help pay for musical instruments in schools.
A new working group will examine the levels different councils charge for music tuition – and in some cases for presentation at music exams.
However, Larry Flanagan, general secretary of the EIS, said performances such as Christmas shows were still under threat.
"All of the good work that goes on in schools is threatened by continuing and short-sighted attacks on music education," he said.
"The postcode lottery of provision that has emerged across Scotland is causing significant damage to the availability of music education for children in some parts of Scotland."
However, Douglas Chapman, education spokesman for council umbrella body Cosla, dismissed the suggestions.
"It is completely wrong to suggest there is a postcode lottery for music tuition. It is also disappointing the EIS have tried to politicise the huge number of Christmas shows and performances that children and teachers are putting on up and down the country."