Playing Guitar By Ear - Listening to the Root note and Perfect 4th

In this exercise, we listen to a root note, and then the perfect 4th of that root note.

A perfect 4th is 5 half-steps, or 5 frets.

The perfect 4th is an interesting concept, because “4th” means like (1st, 2nd, 3rd, 4th),

Literally the 4th note in a scale...

And also 4th is like 1/4th like (1/2, 1/3, 1/4)

If the length of an open string is a root note, then a perfect 4th is 1/4 of the length of the root / string.

However, must consider the functional part of the string. If we fret the string at the 5th fret, we have divided the string into two parts.

The un-used, non-vibrating part behind your finger is 1/4 string length, and the used, vibrating part in front of your finger is 3/4 string length.

So our “perfect 1/4” may actually be 3/4 X root / functional length of string...

Also, the perfect 4th is the fundamental tonal offset between most adjacent strings on a standard tuned guitar or bass guitar.

E-A

A-D

D-G

NOT G-B

B-e

So where-ever you are fretting on the thick E string, you know that the same fret on the A string will be a perfect 4th higher in pitch.

This is helpful because the perfect 4 is a very common interval,

and its also a good anchor point, as you use it as a tonal and physical reference point to know where other notes should be in relation to it.

The perfect 4th is the IV part of the I-IV-V also known as 1-4-5

Also known as 3 chord song, or 3 chord trick

The I is the root note, 1

So all you have left to do now is learn about V, the perfect 5th (7 half steps)