It’s very helpful to know the way notes are distributed over the guitar neck. Having a good understanding of the way pitches are arranged on the guitar fingerboard is essential even for beginners and intermediate players. You gain a lot of useful information by understanding the fingerboard and your playing could be greatly facilitated.
Here is some of the knowledge you gain: an understanding of how open strings relate to different notes at various fret positions; where octaves occur; and patterns of notes that occur in various places on the neck.
Open Strings to 12th Fret. The complete pattern of notes on the fingerboard starts again in the 12th fret. It’s in the 12 fret that the octave is produced above the open string. So, the octave above open string A (fifth string) is found on the fifth string, 12th fret.
Open Strings to 12th Fret. The complete pattern of notes on the fingerboard starts again in the 12th fret. It’s in the 12 fret that the octave is produced above the open string. So, the octave above open string A (fifth string) is found on the fifth string, 12th fret.
Open Strings to 7th Fret. The notes in the 7th fret are a perfect fifth higher than the open strings. For example, the note "D" in the 7th fret on the third string is a perfect fifth higher than "G," the third string open. Perfect fifths are essential to the overtone series and to the formation of basic triads. Note that F# (7th fret second string) is the perfect fifth higher than "B," the second string open.
Open Strings to 5th Fret. The notes in the 5th fret are a perfect fourth higher than the open strings. For example, the note "A" in the 5th fret on the sixth string is a perfect fourth higher than "E," the sixth string open.
The guitar is tuned in fourths, so the 5th fret holds additional importance. Consider the open strings of the guitar from the sixth string down: E A D G B E. One string to the next is the distance of a fourth – with the exception of G to B (a major third). The common tuning practice of moving to the 5th fret then tuning the open string below it works because the open strings are tuned to a fourth.
It may be obvious, but it’s important to realize that the relationship of a perfect fourth remains when playing any two adjacent strings in the same fret. So does the major third when playing the 3rd and 2nd strings. For example, look at the notes in the 10th fret on the image below, D to G (fourth), G to C (fourth) C to F (fourth) and F to A (third), etc.
Here's a link with a fingerboard image to use with the above info.
