About 16,000 music fans are descending on the Glanusk estate, near Crickhowell, for the four-day Green Man Festival which gets under way today.
Tickets for the festival have sold out with top-name acts such as The War on Drugs, Fleet Foxes and Public Service Broadcasting among those performing.
Managing director Fiona Stewart has reaffirmed her commitment to the festival’s independence, dispelling rumours that the festival might be sold to a big company.
She told BBC Radio Wales: "It’s one of the few independents left and we sell out early so it’s a very attractive option to big American, international companies."
"What I love about Green Man is that it enables people to choose their own festival experience.
"They can dance all night, watch comedy or late-night films, or sit in a hot tub drinking bubbly, drink a craft Welsh ale or discover a new band and then go and see an international headliner."
This year’s 16th festival includes an area for stalls selling independently brewed beers and ciders, an area for children and Einstein’s Garden - a celebration of science, art and nature.
Motorists are being warned to expect heavier than normal traffic on the A40 between Abergavenny and Brecon and on the nearby A465 Heads of the Valleys road.
There will also be shuttle buses running from Abergavenny train station.