The standard of bardic circles varies wildly. Some bardic circles are long and are full of talented singers who enjoy historical music. Others are much less formal, and are just full of, well, people who like noise ;-)
Bardic circles are often linked to a circle of entertainers in a particular place, e.g. around a campfire or in a tavern. Some are scheduled as a formal part of an event. Others just happen in some other informal setting or are hosted in someone's home as part of a local group activities.