(I would like to thank the Guitar Handbook for the following excerpt on left-hand fretting techniques)
The function of your left hand is to press the guitar strings down onto the frets in order to sound the required notes. Before your right hand strikes the strings, your left hand must be in position, creating a specific selection of fretted notes for your right hand to play.
Many of the lead guitarist's left-hand techniques - for example, hammering-on, string-bending, slides and vibratos - are all part of the arsenal of tricks associated primarily with the sound of the modern guitar. In contrast, the rhythm guitarist's left hand tends to be more concerned with fingering chord shapes. However, modern rhythm guitarists also use many syncopation and "chop" techniques that rely on the left hand for damping effects. It is, after all, left handed damping that creates specific time values by releasing the strings when it has sounded for the required duration, and that cancels unwanted notes when several strings are played at once.
To play a single clear note without touching any other strings, your fingers should be arched so that the tips come down onto the fretboard more or less at right angles to it. This obviously means that your fingernails should not protrude beyond the ends of your fingertips. You should keep them trimmed.
When you fret a strings, you should hold it down between two frets, but just behind the one you want. The vibrating length of the strings will then be the distance from the higher of the frets to the saddle.
Use only as much finger pressure as is necessary to make the note sound clearly. Pressing too hard will tire your fingers and may hurt. Beginners will experience this immediately-especially with steel strings-since it takes a while to toughen the fingertips and learn how to apply just the right amount of pressure to the guitar strings.
We will get in to more specific style based left-hand techniques in future posts, but that is the foundation.
Good luck, I hope this helps!
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