The Atlantic published this awesome map, which plots the geographical origins of indie bands who played at SXSW last week. The data is not perfect in the sense that it does not include unofficial showcases but it puts Austin in the lead, trailed by New York and Los Angeles. Nashville and London just about tie for fourth place.
SXSW reflects the dual geographies of independent music. On the one hand, large well-established music scenes and centers like New York, L.A., London, and Nashville have the most acts. On the other, smaller college towns do very well in musical acts on a per capita basis. These college towns have two things going for them: They are magnets for musical talent and have lots of young people who enjoy and support live music. These two factors underpin their flourishing music scenes which have given rise to critically acclaimed indie bands.