Definitions come and go, they aren't fixed. My ideal would be an acoustic band in a room small enough not to need amplification. Once electrickery is brought in via a singer's mic, the players want their instruments louder until mutually assured quality destruction occurs.

Since the sixties the electric guitar has become the performance norm with other instruments defined round that standard (and why I recommended the Telecaster as the definitive English folk instrument despite its origins in far away lands) - hence 'unplugged'. I dislike the term because it gives rock bands the opportunity to make hypocritical gestures that suggest they'd have played non-electric instruments for £15 a night all along if it weren't for the maaan insisting they fill stadiums every night.

As someone suggested, avoiding Lynn Truss's finger wagging school maam within all of us is difficult but necessary.