This article is from the Classical Guitar Playing FAQ, by Joshua Weage (firstname.lastname@example.org) with numerous contributions by others.
This is a reasonably controversial subject, with reasonable people
differing in views. There tend to be three broad groups of people -
the 'no posture needed', the 'some posture needed', and the 'exact
posture mandatory for good playing and health'.
What is given here is something approaching the latter. If
you wish to join one of the other groups, just don't do everything
Seating and positioning the guitar
Establishing good seating and positioning of the guitar is fundamental to the
development of technique. Proper habits of sitting and holding the guitar
contribute to basic security, comfort and ease, which bears on all other
aspects of technique.
The general aim of seating is to establish a stable and relaxed position to
serve as a foundation to support the guitar, while maintaining a free and
relaxed posture to provide the best freedom of movement for the arms and hands.
o Begin by sitting up straight and on the edge of the chair. Your back
should be straight, aligning the back muscles with the spine. Your
shoulders should be relaxed and level. Basic good posture is the objective
here: avoid any slouching, leaning against the back of the chair, hunching
or twisting of shoulders.
o Adjust the footstool to about seven inches in height, and place it on
point aligning it with the left legs of the chair, and beneath your left
leg. Place your left foot on the footstool, and adjust the position of
the footstool forward or backward so that the lower leg is perpendicular
to the floor. Also, adjust the height of the footstool so that the upper
leg is pointing very slightly upward (only a few degrees). After the
footstool is properly positioned and the left foot placed upon it, check
again to be sure that there is no tension or misalignment in the back or
The general aim of positioning the guitar is to hold the guitar in the most
effective, comfortable and secure playing position, giving each hand best
access to the strings and to the full range of the fingerboard.
Some terms involved in positioning the guitar:
front: the soundboard of the guitar
side: the side of the guitar
front rim: the joint formed by the front and the side
waist: the inward curve of the sides formed in the middle of the guitar
lower bout: the outward swelling of the sides formed below the waist
o Place the guitar with the waist resting snugly on your left thigh, with
the back resting against your chest. The side should rest flat against
the leg, so that the guitar leans neither forward nor backward. Your
left leg should extend directly in front of you (not to the left), so
that the guitar's soundhole is in the middle of your chest. Rest your
right forearm on the front rim of the lower bout so that the right hand
hovers in front of the soundhole. Be sure to avoid hunching or twisting
the right shoulder.
o Pivoting the guitar on the point where its side rests on your left thigh,
use your left hand to move the guitar's head in an upward/downward arc,
changing the angle of the guitar's neck to the floor. Adjust this angle
so that the guitar's head is at your eye level.
o Pivoting the guitar at the same point as before, move the guitar's head
in a forward/backward arc, changing the angle of the guitar's neck to the
line of your shoulders. Adjust this angle so that the guitar's neck
points slightly backward (only a few degrees).
At this point, the basic position of the guitar is established. To check the
effectiveness of this position, the mobility of the right and left hands must
be checked individually, in case any finer adjustments are necessary.
o Check the right hand position by moving the right forearm upward and
downward from the elbow only. You should be able to comfortably reach
all six strings with the fingers, without raising, lowering or twisting
the right shoulder or wrist.
o Check the left hand position by placing the first finger of your left
hand across the first fret. Slide the hand up the fingerboard, gradually
bending the wrist inward, until the tip of your fourth finger is placed
at the nineteenth fret. This should be accomplished without any strain
or movement in your left shoulder or back.
If there is any problem in accomplishing either of these two checks, there is
probably some need for adjustment of some aspect of the guitar's position.
Each type of adjustment will have the described effect:
o Leaning the guitar forward or backward: Leaning the guitar backward
reduces the impediment of the front rim against your forearm, but it
strains the left hand by causing it to bend beyond its comfortable range.
Leaning the guitar forward produces the opposite effect.
o Raising or lowering the guitar's head: Adjustment of this has little
effect on the function of the right hand. For the left hand, adjusting
this to a lower position forces the left wrist to bend and twist beyond
its comfortable range of movement.
o Moving the guitar's head forward or backward: Pivoting the guitar to move
the head forward improves right hand mobility by reducing the impediment
of the front rim against the right forearm; however, it forces the left
wrist to bend beyond its comfortable range of movement. Pivoting the
guitar to move the head backward produces the opposite effect.
o Raising or lowering the entire guitar by adjusting the footstool: This
adjustment has little effect on function of the right hand. It
significantly affects the left hand's access to the upper frets; if your
shoulder dips or your back leans left to reach these frets, then raising
the footstool can remedy this.
o Moving the entire guitar to the right or left by moving your left leg:
This adjustment has little effect on function of the right hand. For the
left hand, positioning the guitar too far to the left greatly reduces the
ability of the left hand to access the first few frets. If your shoulder
or back twists while reaching these frets, shifting your left leg slightly
to the right can remedy this.
In general, the objective of these adjustments is to achieve a position in
which the right hand can swing freely across the strings without being
impeded by the rim of the guitar, and which gives the left hand the most
comfortable access to the full range of the fingerboard. Some of these
adjustments require a compromise for both hands, some do not. When
establishing this position, commit yourself to a period of continually
practicing it, making adjustments and checking them with the right and left
hand checks. Once you have found it, make the optimum position a habit which
you reinforce every time you sit down with your instrument. If you find
yourself slipping, don't ignore it and pretend it doesn't matter--it does
matter, and the eventual ease and fluency of playing which you can develop
will depend upon it.