24. December 2011 07:02
A perfect Unison (P1) is an interval that consists of two notes of exactly the same pitch. A pair of tones played in unison usually comes from different instruments or human voices. However, since there are up to five locations for each pitch on the guitar, this gives guitar players the ability to play Perfect Unison both harmonically and melodically. Perfect Unisons are also referred to as Unison (the Perfect is implied) or just P1.
The tab below shows the P1 that are used to tune the guitar to standard tuning. Generally P1 are 5 frets apart on adjoining strings. For example, if you wanted to find a Unison for the 7th fret of the A string, you would subtract 5 and move up a string to the 2nd fret of the D string. Notice the Unison on the G string to the B string, it is only four frets; this is because the interval between the E & A, A & D, D & G and B & E strings are all Perfect Fourths and the Interval between for the G & B string is a Major Third. If you wanted to find a P1 for the 15 fret on the G string, you would subtract 4 and move up a string to the 11 fret of the B string.
In our article on Basic Fret Board Memorization we used the “12 Fret Rule” to find the last C note on the B string 1st fret in the tab below. This note could have also been found by using a Perfect Unison by subtracting 4 from the 3rd string 5th fret and moving up a string to the B string 1st fret. If you take the time to study the tab below in detail, you will find that all the unisons hold true to form, the C notes cover a 4 octave range, and as mentioned in the onset of this article one of the C notes can actually be played at five deferent locations on the fret board.