Mercy by Duffy is in C at 126 beats per minute and runs 2:45 across 45 bars. It uses 9 chords — N.C., G, C, G7, Dm, C7, Gm, C9, and a few more. The chord diagram changes as the song plays and the words light up as they are sung, so you can strum and sing along without reading ahead.
Want the melody line note by note? Mercy guitar melody tab.