One of the most common textures in piano music is a slow right hand part with a quicker left hand part, often outlining a self-similar arpeggio whose consistency ties the piece together logically, and whose variation helps to emphasise the harmony of the piece. When arranging piano music of this character for the guitar, there are a few very common problems that occur. I'd like to have a wee look at them, using bars 18-19 of Chopin's Prelude No.3 in G as the basis.
This is the original music written as a guitar part (on one stave and written an octave above natural) We're in the sub-dominant region at this point, and in a few bars we'll prepare for and move onto the last cadence. At the moment though, it looks pretty non-sensical when written out this way, we'd need a lot of extra guitar and a few new hands to play it.
Often the first step in arranging piano for the guitar is to move one of the hands a whole octave. Depending on whether you're transposing (we're not here), it's usually pretty obvious which hand to move, one usually drops the right hand, but that lowering is somewhat offset by the brighter tone of the guitar. Often various sections of a piece will have to remain and others moved up or down, and that presents its own set of problems. Another thing that is usually helpful is to get rid of doubles, which we've done here, as the low E is not a significant voice in the piece. The problem is; the low C in what was the left hand part is still a major third below the low E of the guitar. We'll have to do something about that.
(ps - the overlapping of the G in the right hand melody with the A and G at the top of the left hand melody is a crack one has to smooth over in performance).
Leopold Godowsky's arrangements of Chopin for the left hand only have been invaluable in suggesting ways in which the character of a piece can be preserved even while condensing it drastically. A technique that he is often forced to use is to eliminate the first note of the left hand part, before jumping down to continue the lower melody (see his version of etude 6, op.10). I've also seen Mahler use this left hand rest in arrangements of his own pieces for piano. If you do utilise this approach, the next problem is that you then have a melody whose lowest note is the fifth of the chord, and we don't want this to sound like a 6-4 chord. One advantage is that left hand parts like this are often spread out in the lower register, meaning that you can replace a melody such as C₂,G₂,C₃,G₃... with rest,C₃,E₃,G3... with only a small change in the character of the melody. In this case that isn't possible, so...
We reinstate the root, but an octave above. This might be better, but in my opinion this is a rather ugly solution, with the low G still being conspicuous after the root.
This is my preferred solution to this particular problem, a quasi-turnaround of a B after the root, creating a more sinuous melodic effect in keeping with the curvaceous feel of the piece. The G at the end of the bar is retained to create a stronger dominant effect.