Filk is music by and for science fiction and fantasy fandom. Often performed at sci-fi conventions by people with little talent, but a healthy respect for each other's lack of talent.

Almost anything is game for filking -- political songs, space songs, cat songs, story songs -- everything from parodies of popular music, to rescanning existing lyrics to new tunes, to completely new lyrics and new music.

People who filk are called filkers; these are some of the most astoundingly intelligent and creative folks you'll ever meet. And some of the most interesting people you'll ever meet, as well. People like Leslie Fish, Bob Kanefsky, Julia Ecklar, Kay Shapero, Mary Creasey, Steve Savitzky, and Kathy Mar... who are mostly libertarian, or at least for freedom.

When filkers get together to sing, it's called a filksing. There are several different styles of filksing -- bardic circle, poker chip bardic circle, khaos (also called chaos), moderated khaos, and variants of these. The basic rules of a filksing are that, when it's your turn, you have three options: pick, pass, or play. To pick means that you choose a song that you want to hear, and others in the filksing sing it for you. To pass means that you pass your turn, and to play means that you will play/perform a song for everyone else participating. The various styles of filksing are basically changes in the way that people are given turns.