This song is about as simple as it gets, using only 1, 4, 5, and 6.
"I Will Rejoice" by: William Murphy
Key G LH/RH
Part 1:
G / D-G-B There is a fountain,
G / D-F#-A so full of grace that
G / C-E-G flows from Emmanuel's
G / B-D-G veins,
(repeat)
Part 2:
G / D-G-B I will
F# / D-F#-A rejoice,
E / B-E-G I will
D / A-D-F# rejoice,
C / G-C-E and be glad.
G / B-D-G
(repeat)
This is how I play it, but you can use different inversions of the above chords as you see fit. It's basically "Let It Rise" Part 2, LOL.