i dont think there ever was an acoustic version of earth wind and fires classic september,
but i love the song and i love playing acoustic covers of songs,
and this is what i worked out to be right...    
    (this may be a bit off key, but just change the vocals to fit)

(dont start playing until syllable 2 of remember)

          E        A     G        E
Do you remember the 21st night of september?
         A            G           E
Love was changing the minds of pretenders
      A          B       F#  
While chasing the clouds away

Bridge: F# G A

                E
Our hearts were ringing
       A            G           E
In the key that our souls were singing.
      A             G
As we danced in the night,
   E             A               B      F#
Remember how the stars stole the night away

        F# G A

E          A            G
Ba de ya - say do you remember
E          A            G
Ba de ya - dancing in september
E          A            B      F#
Ba de ya - never was a cloudy day

        F# G A

                E
My thoughts are with you
        A               G                 E
Holding hands with your heart to see you
      A            G
Only blue talk and love,
   E            A             B        F#
Remember how we knew love was here to stay

        F# G A

      E                A             G                   E
Now december found the love that we shared in september.  
     A             G
Only blue talk and love,
   E         A            B       F#
Remember the true love we share today

        F# G A

E          A            G
Ba de ya - say do you remember
E          A            G
Ba de ya - dancing in september
E          A            B      F#
Ba de ya - never was a cloudy day

E          A            G
Ba de ya - say do you remember
E          A            G
Ba de ya - dancing in september
E          A                  B       F#               F# G A  E ...
Ba de ya - golden dreams were shiny days