How often have we witnessed some astonishing performer and rushed out to buy their album - only to be bitterly disappointed when it sounds nothing like the transcendent live experience of the day before? The conventional approach is to recruit a conventional band of musicians to lay down a backing track as the hapless songwriter strums his or her way through the song, then layer the whole thing up with other instruments. Tasteful electric guitars usually produce the stodgy even consistency known as soft rock. For folk rock sprinkle liberally with mandolins and fiddles; add sax and a few open electric piano chords for jazz rock. There's also the (quite unrelated) jazz trio approach, where the artist's own playing is placed centre stage accompanied only by the woody thud of an upright bass and unobtrusive sound of drums being tickled with brushes somewhere in the background.
I agree, though this does sound a bit like the "Support Act CD" problem. There can be any number of reasons why a band might sound great on the night and none of those reasons have to have anything do with how the music actually sounded -- go over to the Internet Archive and download some bootlegs if you don't believe me, there are plety of concerts there that must have been fantastic to be at, but in the cold light of day are not that great -- and at that moment you hand over your tenner for the Support Act's CD you probably have less idea how it's going to sound than you did before you read their name on the poster outside ticket.