SIPTU and the Musicians Union of Ireland (MUI) have warned management of State broadcaster RTÉ against a review of its orchestras.
The unions say RTÉ could face "significant opposition" to the process.
The broadcaster has announced an independent review of its orchestral services.
The review will look at the best way of providing quality and sustainable orchestral services to the Irish public.
It will cover both the RTÉ National Symphony Orchestra and the RTÉ Concert Orchestra.
The review will be led by former director of BBC Radio and of BBC News, Helen Boaden.
RTÉ's 2014 annual report showed its various orchestras cost €11.56m in total, employing 209 people.
RTÉ says while it is the biggest employer of musicians in the country, its financial circumstances "remain challenging".
Aodán Ó Dubhghaill, head of RTÉ Orchestras, says: "Through my work with colleagues in the European Broadcasting Union I can see that orchestras across Europe are suffering cuts to their funding, reflecting the threat to public service media globally.
"RTÉ's overall funding position is well known and it is incumbent on RTÉ to consider and assess its role in the provision of orchestral music as it plans for the future.
"In this context, this review will look at what our current and future audiences want, how they will engage with us and how RTÉ's orchestral music will be heard in venues, on screens and on radio right across the country."
File photo of the RTÉ campus
SIPTU organiser, Graham Macken, says: "While RTÉ has stated repeatedly that all the constituent unions represented within the RTÉ Trade Union Group will be consulted at every stage of its proposed restructuring programme, the MUI which is affiliated to SIPTU only became aware of the decision to conduct this review through unofficial channels."
SIPTU says representatives have written to RTÉ management, outlining "frustration of our members" at learning of this development third hand.
He adds: "There are a number of vacancies within both orchestras that remain to be filled for quite a considerable time, at this stage.
"Our members expect these roles and any additional vacancies that may become available as a consequence of the current voluntary exit package to be advertised without delay.
"SIPTU members have warned management that any attempt to unilaterally alter the structures or terms and conditions within the orchestras could trigger a significant opposition. Our members are not ruling out potential industrial action at this stage."