To learn Billie Marten - La Lune chords, your first step should be understanding these chords - G, Em, Bm, D, G, Em, D and Bm in sequence. I suggest starting at a calm pace of 53 BPM, and as you gain confidence, approach the song's BPM of 107. With the song's key of D Major, set your capo to fit your vocal range and chord choice.