Featuring the 30 or so voices of the Blaenavon Male Voice Choir, the charity concert, which begins at 7pm at WS Layton Farm, will also also offer traditional music from the Llandrindod Silver Band plus the popular songs of local Thornbury-based singer Lisa Legge.
“We are catering for all age groups," said host and organiser William Layton, who has cleaned out a big barn to stage the event.
“Personally I am a fan of Welsh choirs and Lisa has a lovely voice and is much in demand to sing at functions around the locality
“We have also attracted the talented musicians from a silver band.”
It is a first for the Llandrindod Silver Band, who have never shared the bill with either the Blaenavon Choir or Lisa before.
Mr Layton, who is president of the BVMC, said his choir had offered to sing for free to help boost the funds of the two chosen charities and the other entertainers also offered to waive their fees.
“We are hoping to raise a good sum for the British Heart Foundation as well as the Herefordshire-based mental health charity, We Are Farming Minds," he said.
“We are so grateful to all local farm producers and organisations who are giving produce and drinks so that a good and affordable family outing is available to all.”
Tickets at £10 are available on the door on Saturday. The first drink is complimentary, generously given by local breweries, cider makers and soft drink manufacturers.
Children go in free, and strawberries and crisps will also be given to the youngsters.