Sus4 chords are formed with the second note in the chord raised one step. In addition to sus4, there is sus2. In the case nothing more than "sus" is mentioned, for example Dsus, it's normally sus4 that is intended. See also common sus chords.
The sus4 chord is very close to the original major chord because only one note is changing. A comparison of C major and Csus4:
C major Csus4
There are two differences: 1) on the fourth string the tone is raised one semi-step from E to F, 2) you don't play the highest open string since this is an E note. When shifting from C to Csus4 you only need to add the little finger (4) and you don't move the rest of the fingers.
A common alternative fingering for Csus is X33011, which can be advantageous in progressions such as F - Fsus - Csus. Two alternative chord shapes of the suspended chords is Esus4 as 002200 or 002400. An alternative fingering for Asus4 is X00230.
Chord constructionCsus4 x - C - F - G - C - x
Dsus4 x - x - D - A - D - G
Esus4 E - B - E - A - B - E
Fsus4 x - x - F - Bb - C - F
Gsus4 G - x - D - G - C - G
Asus4 x - A - E - A - D - E
Bsus4 x - B - F# - B - E - F#
Guitar versions of the chord
Notes in chordCsus4 C - F - G
Dsus4 D - G - A
Esus4 E - A - B
Fsus4 F - Bb - C
Gsus4 G - C - D
Asus4 A - D - E
Bsus4 B - E - F#
The intervals are 1 – 4 – 5
A common practice is to alter the major with a sus chord, as in the sequence D - Dsus4 - D.
In the Tom Petty tune "Free Fallin'" a certain chord progression is used in a big part of the song:
D - Dsus4 - D - Asus4
Another progression with sus4 chords is this one:
E - Esus4 - E - D - Dsus4 - D - A - Asus4 - A
It's rather common to use the sus4 in the end of the verse to anticipate the chorus, a so-called imperfect cadence. One example of this can be found in the verse of "I Will Survive":
Am - Dm - G - Cmaj7 - Fmaj7 - Bm7b5 - Esus4 - E
This progression uses the suspended chord for the transition:
E - Esus4 - F#m11 (202200)
This progression use the suspended chord for creating extra tension before the major:
Asus4 - A - F#m7 - Bm7 - Esus4 - E
The suspended chords can be played inverted, some fingerings are presented here:
Note, that Dsus4/G is identical with Gsus2.
Some fingerings with alternative bass notes are presented here:
Note, that Esus4/F# is identical with Asus2/F#.
Sus chords with sharp or flat root
F#sus4 / Gbsus4
G#sus4 / Absus4
A#sus4 / Bbsus4
F#, G# and A# sus4 uses the same shape as Fsus4 (see above). The same shape can, of course, be used for C# and D# sus4 also.
Other flat and sharp suspended chords shapes
Not so common are sus chords with root notes consisting of flat or sharp notes, partly because the shapes often are inconvenient. Here are nevertheless some additional examples:
C#sus4 / Dbsus4: 444XXX
D#sus4 / Ebsus4: X11344
The connection between sus4 and add4
The sus4 and add4 chord types are similar, but the difference is that sus chords include three notes whereas add4 chords include four notes:
Csus4 (C-F-G) - Cadd4 (C-E-G-F)
Dsus4 (D-G-A) - Dadd4 (D-F#-A-G)
Esus4 (E-A-B) - Eadd4 (E-G#-B-A)
Fsus4 (F-Bb-C) - Fadd4 (F-A-C-Bb)
Gsus4 (G-C-D) - Gadd4 (G-B-D-C)
Asus4 (A-D-E) - Aadd4 (A-C#-E-D)
Bsus4 (B-E-F#) - Badd4 (B-D#-F#-E)
A moveable shape is 113211 (Fadd4).
The suspended 4th is neither major or minor. The chord can be written as msus4 (minor sus4), but this is actually the same as sus4, but may be written this way because of the context is minor.
Back to sus chords