This is a list of jam band music festivals. This list may have some overlap with list of historic rock festivals and list of reggae festivals. Jam bands are musical groups who relate to a unique fan culture that began in the 1960s with Grateful Dead (see deadheads), and continued with The Allman Brothers Band, which had lengthy jams at concerts. The performances of these bands typically feature extended musical improvisation ("jams") over rhythmic grooves and chord patterns, and long sets of music that can often cross genre boundaries.