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4 chord repeating pattern with optional slash chord in bar 4. The tempo is slow so the chords change every two beats, the slash chord falls on beat 4 of bar 2:
//:Am Dm /G C (C/B) ://
A slash chord means a chord with a different bass or lowest pitched note, instead of the usual root note. C/B means a C chord with a B bass note, instead of the root C.
Not chords invented by Slash from Guns n’ Roses as I believed when I first started guitar!