The chords below are shown, for simplicity, as if you were not playing the A bass note. The bass note holds on the A (open A string) note through the all of the chords during the intro and verses if you are fingerpicking. If strumming, I would just play the 3 high strings throughout the verse. This song uses 4 different shapes for the A chord. I noted them as A, A*, A** and A*** Chord shapes used in the intro and verse are: A** Bm7 A* Em7 e|--9-------7-------5-------O---| B|--10------7-------5-------3---| G|--9-------7-------6-------4---| D|------------------7-------5---| A|------------------------------| E|------------------------------| with a little work you can figure out the hammer ons and pulloffs to make the melody The chord shapes used in the outro and the break are: F#m C# F#m7 B E11 Bb A*** e|--9--------9-------9-------7-------7-------6------5---| B|--10-------9-------10------7-------7-------6------5---| G|--11-------10------9-------8-------7-------7------6---| D|--11-------11------11------9-------7-------8------7---| A|--9--------11------9-------9-------7-------8------7---| E|-----------9---------------7---------------6------5---| A** I thirst but never quench Bm7 I know the consequence, A* Em7 feeling as I do A** We're in a spinning top Bm7 Where, tell me, will it stop A* Em7 And what am I to say A** Open our music book, Bm7 that only few can look A* Em7 And I'll write a song for you, oooooh A** Bm7 Bm7 Dmaj7 Bm7 A* hoooooo A** Love is a symphony, Bm7 hearts in one melody A* Em7 'Cause I write a song for you A** Sounds never dissipate, Bm7 they only recreate A* Em7 In another place A** There in your silent night Bm7 Joy of a song's delight A* I write a song for you Em7 You write a song for me F# Bm E we write a song for loooove of A Looooove F#m C# pah padah paaaah F#m7 B pah padah paaaah E11 Bb A*** pah padah paaaaaaah aaaaaaaah A** My magical mystique, Bm7 A* finding it all complete Em7 In a lovely face, A** feeling we try to chase Bm7 A* Memories that won't erase, Em7 stay forever new A** We have a magic box Bm7 in which is never locked, A* and I'll write a song for you. Em7 You write a song for me F# We'll write a song, of Bm C#m D Love E Of F#m C# F#m7 B Love E11 Bb A**** {outro} F#m C# F#m7 B E11 Bb A**** (repeat ad nauseum)
Source: https://tabs.ultimate-guitar.com/tab/earth_wind_fire/ill_write_a_song_for_you_chords_2101651