Suspended Chords
Suspended chords replace the 3rd with either the 2nd (sus2) or 4th (sus4). Since the 3rd determines major vs. minor, removing it creates an ambiguous, floating sound that wants to resolve.
Sus4 and Sus2
The sus4 chord [0, 5, 7] replaces the 3rd with the 4th. The 4th has a natural tendency to resolve downward to the 3rd, creating the classic sus4-to-major resolution. This is one of the most recognizable sounds in rock — the opening of "Crazy Train" by Ozzy Osbourne and The Who's "Pinball Wizard" use sus4 resolutions.
The sus2 chord [0, 2, 7] replaces the 3rd with the 2nd. It has a more open, modern sound. Interestingly, a Csus2 (C-D-G) contains the same notes as Gsus4 (G-C-D), giving it a dual identity that adds to the ambiguity.
Why Suspended Chords Work
Suspended chords create a moment of tension or anticipation without committing to major or minor. A songwriter might hold a Dsus4 for a beat before resolving to D major, creating a small moment of tension and release that adds movement. They appear frequently in pop, rock, and film scores precisely because of this ambiguous quality.
In ChordColor
On the color display, a sus2 shows Red (root), Orange (major 2nd), Blue (perfect 5th). A sus4 shows Red, Lime-Green (perfect 4th), Blue. The absence of yellow (major 3rd) or amber (minor 3rd) visually confirms the "missing third" that defines suspended chords.