The Perfect 4th. Suspended 4.
This interval is found by adding the 1st and 4th degrees of a major scale.
Used in context of a chord, the Sus4 chord is a great representation.
Exactly like our sus2, the sus4 is a Major chord whose 3rd has been replaced. Only in this case, by the 4th degree, not the 2nd degree like in our last lesson.
The Formula for a sus4 chord is: 1 4 5 7 or simply 1 4 7. The 5th can be omitted depending on how you wish to voice the chord.
Just as we saw earlier, the 2 and 9 are the same note. The 4 and 11 are also the same note. So when building a sus 4 chord. you can use combinations that include the 11th scale degree as well as the 4th. Just make sure you don't play that Maj3rd.