If you are playing Zydeco, you are probably talking about an electric guitar. I don't know that I would capo an electric. I would just play barre chords and partials. If you do capo, especially on an acoustic guitar, I would try to stay as close as possible to the end of the neck so the guitar doesn't get too twangy.
If you capo the first fret, Bb would be played in the A position, and F would be played in the E position. If you cap at the third fret, Bb is in the G position and F is in the D position. I think third fret is most common because when playing in the E position, you have to play a B7 or barre a C when your chord changes to C. Did I confuse you enough?
In accord with what Larry said, most Zydeco will be in the pull, or key of F. I would just play an open, or choked F and slide up to the Bb when needed.
Last week, I had a party gig. We use different guitar players from gig to gig, and I noticed that the guy we had that night was using a capo on his electric guitar. Since I use an Bb single row, and an F-Bb-Eb triple row, many of the songs end up in the key of F. Not surprisingly, the capo was on the first fret. I did not notice any ill effects from the use of a capo on an electric.
I can't recall any other electric guitar players I have worked with using a capo, but I don't have a problem with it.
Hasn't Keith Richards always used a capo on his guitar? I remember the first time I noticed it, and I think he had it up pretty high on the neck - like on the 7th fret.
The April 2011 Dewey Balfa Cajun & Creole Heritage Week
