First up is a G major triad. If you can reach this fingering comfortably, play it with fingers 1 (your thumb), 2, and 3 of your right hand. The next chord is a C major triad in second inversion. Keep the G on the bottom of the chord, and simply move the top two notes up to the nearest white keys. Sometimes you’ll see this on a chord chart written C/G, which is called a slash chord. So called because of the slash separating the two note names, the name of the chord is on the left of the slash, and the bass note is on the right of the slash. As though it were a fraction, think of it as a C chord over the low note G.
Next, we have a G7 chord voiced with no third; since the G harmony is still carrying through, your ear probably still hears this as a dominant seventh chord. A dominant seventh chord has a major triad plus the minor seventh above the chord root. The full G7 chord is shown for reference in Example 4. The chord figure in the main riff of “Mercy” comes back down to the C/G chord and returns to the G triad before repeating.
To get a sound similar to that used on the track, find a retro organ patch on your synth. If your keyboard has banks of sounds, find the organ section and look for patches with names like “combo,” “surf,” “60s,” “Farfisa,” or “Vox.” If you have a Hammondtype organ sound (or preset with a name like “jazz organ”), you can get the “Mercy” sound by turning off any rotary or chorus effects and adding a little bit of overdrive for some funky grit. Yes, yes, yes