Punkfolk: While we're talking about guitar as accompaniment, it's worth mentioning that other instruments may fit particular songs better. Guitar has a fulness to it that a mandolin or banjo doesn't have, but there are some songs where a banjo gives a drive and energy and enough space between notes to make it better for that particular song.

Now, this being the Land Of Crinkled Noses, I should add that I found it impossible to accompany black gospel on an acoustic guitar, and use an electric for the sustain and the ability to project loud enough to be heard. The first time I tried leading black gospel playing guitar, I just took the strap off over my shoulder and put the guitar down after a couple of bars of such full-throated singing. I couldn't hear my guitar at all.

Electric guitars are especially good for blues where you need sustained notes to harmonize with the vocal, and bends of the strings to match bent notes of the singer. Acoustic guitar sounds best to my ears on the old country blues, because they don't need the same sustain (and they are usually sung without a lot of other instruments or voices to drown out the guitar.)

Jerry