Originally an African instrument brought to America during the slave trade. The banjo is the four-string variety (as opposed to five strings in the southern USA and ballads) and is tuned to G,D,A and E like the fiddle, except it is an octave lower. It was a controversial instrument in traditional circles for many years as it was considered to be an intruder to the tradition.
It would be impossible to overestimate the contribution of individual instrumentalists to the long running and continuing success story that is the Dublin Traditional Musical Pub Crawl, although were you to meet some of said performers in a social setting you may well doubt their ability to contribute to the success of any venture not involving the sale of alcohol, the ascerbic overuse of cynicism or the rebirth of consequence free hedonism.
These are (almost) their stories.