I want to play a four-chord song: D -> A -> Bm -> G -> repeated.
D, A, and G are all open chords -- and B minor is a 5-string barre chord.
I'm practising (only having trouble with) the "A" to "B minor" chord change.
My difficulty is finding it (the strings for Bm) fast enough -- i.e. to complete the chord change from A to B minor in less than about half a second.
I can play Bm fine once I get there -- now I can change chord from A to Bm reliably in a bit less than one second, if I look at the strings.
I think my trouble is finding the right strings (i.e. index finger on the 5th string, middle on the 2nd, ring on the 4th and pinkie on the 3rd) -- unless I'm careful (and slow, and look at and adjust what I'm doing) my fingers go on the wrong strings, too high or too low.
I think the reason why I don't have that or any trouble with other (open, non-barre) chords (such as G, D, C, A, and E) is that my thumb is on the edge of the neck (i.e. on the top of the neck when the neck is horizontal and facing forward), so I position my fingers by feel relative to where the thumb is anchored.
However for a barre chord, my thumb is on (it moves to) the back of the neck (i.e. somewhere behind the neck as you look at it), it's moving (from the edge for the "A" to the back for the "Bm"), and thus isn't a reliably-positioned anchor relative to which I can position fingers.
How or relative to what do you position fingers and/or thumb and/or the hand on the neck, when moving to a barre chord?
I'm using a steel-string acoustic guitar (with the neck at about 45 degrees from vertical, standing and with a strap).
I've seen YouTube videos on how to make the barre chord shape, which give tips on how to press the index finger, position the elbow and the thumb -- but I don't know one on how to find the right strings quickly.
To be clearer about what I think the problem is: having practised, I more-or-less know and easily find the hand shape for the chord, what I can't find quickly is the hand position relative to the neck.
For the open chords, the thumb is on the edge of the neck, so each finger can find their string by feeling how far each finger is from the thumb.
Also the lowest portion of the index finger may be touching the other edge of the neck (which again gives tactile feedback about the position of the hand relative to the neck).
Whereas in the two barre chords i.e. F and especially Bm, the thumb is round the back -- and the back is smooth, rounded, featureless -- so the whole hand is lost in space, and doesn't know where it is relative to the neck.
The hand is moving a lot, too, for the transition: fingers are pointing almost vertically down the neck (all lined up on the 2nd fret) for the A chord, and horizontally across the neck (on the 2nd through 4th frets) for the Bm. For the open chords at least the thumb is in a more-or-less constant position, a kind of anchor.