The suspended chord (sometimes called a suspended 4th chord) is constructed from the major scale using the first (1), fourth (4), and fifth (5) notes of the scale. The symbol for this is the letters sus (or sus4), placed after the letter name of the chord. There are two inversions for each suspended chord that you should practice and become familiar with, using both left and right hands. This is a major chord with the fourth substituted for the third.
In root position:
Symbol Notes in Chord
Dsus D G A
Asus A D E
Gsus G C D
Fsus F Bb C
Unlike the V7th chord, which leads back (resolves) to the I chord (In the key of C, G7 resolves back to C), the suspended chord resolves to the same major chord it is derived from. Gsus resolves to G, Dsus resolves to D, regardless of the key of the chord progression. Sus chords are useful for making accompaniment more interesting when there are long passages of a song using one chord. Instead of playing a C chord for eight bars, you could add a few Csus chords.
So, here are more sus4 chords in root, first and second inversion.
Dsus4 = D G A
Dsus4 = G A D (first inversion)
Dsus4 = A D G (second inversion)
Then, we have:
Dbsus4 = Db Gb Ab
Dbsus4 = Gb Ab Db (first inversion)
Dbsus4 = Ab Db Gb (second inversion)
D9sus4 = D G A C E
Now, we have:
Esus4 = E A B
Esus4 = A B E (first inversion)
Esus4 = B E A (second inversion)
You can listen to suspended notes in use in songs like Free Falling by Tom Petty. They are useful when you have a song that makes use of one chord for a long time. You can also listen to suspended tones in worship songs like Jesus Mighty God.
Suspended second chords are merely inversions of suspended fourth chords. These chords are often found in folk music & popular music. A jazz sus chord is a dominant seventh chord with an added fourth (Gsus, for example), & may be written as a slash chord (F/G, or even Dm7/G) so as to show its function in II-V-I progressions.
Give it a try. The suspended triad will provide a cool tension and spice to your playing.