The Guitar Teacher Tuner:

     To sound the selected string, press the button with the quarter note on
the button's face.  To stop the sound, press the button with the quarter rest
on its face.  Selecting a new string starts the sound automatically.

     Any time a new frequency begins to sound, it will last up to 60 seconds
if the tuner is left untouched.  To restart the sound, press the quarter-note
button.

Tuning:

     If you have trouble tuning your guitar, you're in good company.  Most
people including many professionals have a love/hate relationship with their
instruments because of tuning problems.  In most cases, it's because the
guitar was not set up right in the first place, and is actually impossible to
tune correctly.  But, even if everyone was given a perfectly adjusted
instrument, it's doubtful that one in a great number could properly explain
how to tune it.  Many know various ways of getting the instrument into some
kind of acceptable shape, but most methods are faulty.

     The most common method of tuning is actually a very poor one.  Most
guitarists learn early that the first string open (E, the thinnest string) is
the same pitch as the second string at the fifth fret.  One starts by hoping
that the first string is close to being in tune, and then if the second
string, fifth fret can be tuned to sound the same as the first string open,
then the second string it is reasoned must be in tune as well.  After
comparing the second string with the first, the third string is compared with
the second and so on until all of the strings are in tune.

     There are at least two problems with this method.  First of all, most
guitars, especially acoustics, don't have their bridge "saddles" set at the
right distance from the top nut, so when the second string was played at the
fifth fret, it probably wasn't perfectly in tune and therefore not a good
reference.  Secondly, our hearing is not perfect and even when we think two
notes are perfectly in tune there is still a certain amount of error.  As you
move across the neck toward the sixth string, your error is compounded.  How
many times have you used this method, thinking you did a good tuning job and
then when you played a chord it sounded terrible?  That's because when you
tuned the second string to the first, you were just a little out, but by the
time you got to the sixth string, you were a long way out.

     When tuning, it's best if you tune every string to the same note instead
of several different notes that get gradually more and more out of tune. 
This can be a little tricky and demands considerably more knowledge. 
However, with the Guitar Teacher tuner you don't have to worry about the
problems of tuning to inaccurate notes.  Also, you're not tuning the strings
at the fifth or any other fret--you tune them as open strings.

     So how does one know when the string is actually in tune with the tone
from the computer?  Most people can tune it so it's close, but there's a way
to be very precise.  When two notes are close to the same pitch, but not
quite, you should hear a faint pulsating sound.  As the notes get closer to
being the same pitch the pulsating slows down, and the goal is to make it
stop altogether.  When it stops, the two notes are vibrating at the same
number of cycles per second (Hertz or Hz).

     If you find that later, a string seems to have gone out of tune, go back
to the tuner.  Tuning to another string which itself might be a little out is
where you begin getting the whole thing in a mess again.  If your tuning
still seems inaccurate, it may be that your bridge and/or top nut are not
adjusted properly (this is a common problem).  You might consider taking your
guitar to a repair shop for an opinion.