Borders beyond bluegrass - and bluegrass beyond Kentucky

The BIB editor writes:

To the perennial question 'What is bluegrass?', there's now an answer which may not be conclusive but is pragmatic and useful - 'Bluegrass' = any music played by a band that gets an enthusiastic reception at a bluegrass festival.

One example is Matuto (USA), who play 'Brazilian bluegrass' with electric guitar, piano accordion, bass, drums, violin, and Brazilian percussion instruments. There's no connection, as far as we know, with the São Paulo Bluegrass Music Association, and it can be hard to hear the connection with bluegrass; but it must be there somewhere, because their performance at (for instance) the 2013 Wintergrass Festival was warmly commended by the organisers, audience members, and other artists (see this video from their YouTube channel).

Matuto founder member and guitarist Clay Ross is quoted on Bluegrass Today as saying: 'I’ve heard Bill Monroe would tell musicians, "You can’t really play bluegrass because you’re not from Kentucky, you should do what you do.”' Bill Monroe certainly believed that people should play their own style; but if he ever did say that non-Kentuckians couldn't play bluegrass, he didn't let this affect his choice of band members. Of the 149 Blue Grass Boys listed in the appendix to Tom Ewing's Bill Monroe, twenty-eight were born in Tennessee, and only fourteen in Kentucky - less than North Carolina and Virginia with twenty each. In both the 'classic' band of 1945-8 and the last version of the Blue Grass Boys with which he ever recorded - let alone his other bands - Bill was the only Kentuckian.