By analyzing the construction of both chords, sus2 and sus4, we saw that each are essentially the same chord. There are two intervals of fourths connecting the three notes together. The main difference between them - sus2 and sus4 - is the note on which you begin. The construction of straight fourths also implies a secondary harmonic function of them being neither major nor minor. Applying these chords within its surrounding melodic context, the arrangement and harmony, will help to balance the overall amount of major or minor desired throughout the ensemble.
Sus2 chords will make it less minor. Sus4 chords will make it more major. In the color wheel of music, sus2 is subtractive; sus4 is additive. By using a different way to arrive at the same answer, less minor can create the same result as more major. These relationships however, are non-linear, nor polarized black and white. There's everything in-between. Different shades of gray are added to, or subtracted from, white or black to widen the tonal palette of sounds available. Its function could be likened to the contrast control on your computer monitor.
As a thought experiment, if you have ever dabbled in black and white photography, imagine placing a solid color filter on your lens to create a specific effect. Different color filters affect the recording of gray to film differently. Sometimes, it is desirable to stack more than one filter together. In every case, the intensity of the light entering the lens aperture has been altered, so in order to maintain a proper exposure - the overall amount of light captured to film - you must compensate for that loss of lumens by manipulating the other controls of exposure available on the camera. The process of compensating for one variable by manipulating others is a skill which can applied to music. Group improvisational scenarios, as well as writing and arranging, are great places to experiment with these tools.
Below is a familiar-sounding example of the suspended chord in action. A four chord tag you'll hear in many folk-style songs, this progression compliments a waltz - i.e. 3/4 time-signature. Try it with a few different rhythms. Remember, almost all chords are slidable. You can move the whole shape up and down the neck, maintaining that chord formula under a different root name.
The next progression is similar to the last, but is rhythmically different, and is also in a different key. The chords have a "stepping-stone" kind of feel to their melody, the second group of four chords responding to the call from the first group. It features a chorus-like melody to the changes. Try this initially as a slow 2/4. Every chord shall receive one beat of time. You can start by just counting 1-2-1-2-1-2, and so on. When you get bored of that, try the same thing again, only this time swing it by making the two beats unevenly weighted.
The 1 beat could be divided into three parts; the 2 beat could be divided into two halves. E.g., 1-e-a-2-and, 2-e-a-2-and, etc. There are still two beats, but the 1 beat is more dominant than the 2 beat. When three measures like this are grouped together, the time signature could then be argued to be 9/8. Three, 1 beats per measure. By extending the length of a quarter note to be a dotted quarter note, one can choose to subdivide the three beats-per-measure differently than in 3/4 time, changing time signature and meter without changing the overall BPM (tempo). Try switching back and forth between  -  -  and [1..2.] - [2..2.] - [3..2.].
The progression underneath is an example of melodic movement by voice-leading. The progression has a 7/8 feel to it, which breaks into 3 in the front and 4 in the back. Six, E chords climb up the neck to then fall gently onto the major-seventh, where it stays stagnant for a whole bar before looping back. Listen to the melody and timing interacting with the way individual notes are picked. Try separating the bass line from the melody line, bouncing off of each other and the remaining strums of the chord to the rhythm over a bar of time.
This last progression is an example where the sus4 chord is used to supplement a dominant V chord in a minor blues progression near the turnaround. In B.B. King's, "The Thrill Is Gone," you will find these chords. Many minor blues progressions with a Latin-style of rhythm (cha-cha, samba, rumba, etc.) will feature a similar kind of chording near the turnaround. In many minor blues progressions, the VI chord (A minor in the key of C) is also the I chord. VI-II-III, can be equal to, I-IV-V.
About the Author:
Dealey is a Vancouver, Canada based guitarist, songwriter, recording engineer and producer. He is the author of the forthcoming independent book, The Relative Nature of Chords: A street-smart field guide for guitar. Watch for exclusive excerpts on Ultimate-Guitar! You can support his ventures by buying his music here - or talk to him about collaborating on your project by email to: info(a.t.)aurora-studios.ca