The grandest of them all and the originator of many specialized tribute festivals that follow the "something by something something" format, South by Southwest, aka SXSW, has been a major gathering place for unknown acts, up and coming acts, or acts that are just about to break out. There was a time when the festival was courting big names as well, but they have pulled back since and stuck to to the formula that makes it a unique experience: scheduling 2,000+ relatively little known bands and artists spread across town throughout a week in March. The festival has also created a secondary layer of unofficial spotlights for acts that come to town to perform in unaffiliated venues as well, which leads to every bar, every venue, every hotel lobby, and every open space taken over by musicians of all stripes and genres hoping to get some industry buzz going. This is the festival that unofficially kicks off the festival season and sets the tone for the rest of the year.
SXSW also hosts major music industry oriented talks and conference presentations around the same period, keynote addresses, public discussions for activists, a film festival, comedy festival, and multimedia/game/social media/tech convention at the same time, for those who are in town for reasons other than music.