The initial section of the intro is really quick and is probably an ad-lib from Freddie  
all based around E, E7sus4 and E7 with runs down through the scall with a few trills in it. 
Then the main intro starts, continuing through the song. 
Eb5   Bb5  C5 
 
C5 
    Another party's over 
G5 
    And I'm left cold sober 
  F#5           F5          E5 
 My baby left me  for somebody  new 
F5 
    I don't want to talk about it 
Ab5                               Eb5    F#5 
    Want to forget about it, wanna Be intoxicated with that 
 F5     Bb5      
 Special brew  
                Eb5       G5 
So come and     get me    Let me 
Ab5            Ab5 
   get in that sinking feeling 
Eb5              F#5          F5 
   that says my heart is on an all-time low 
   Bb5              Eb5 
   So        don't expect me 
G5 
   To behave perfectly 
Ab5               Ab5 
   And wear that sunny smile 
Eb5          F#5 
   My guess is I'm in for a 
   F5 
   cloudy and overcast 
F#5 
   Don't try and stop me cos I'm 
   Eb5            E5           F5     F5    F5  F5 
   heading for that stormy weather soon  
Ab5 
   I'm causing a mild sensation 
Ab5 
   With this new occupation 
Eb5              C5 
   I'm permenantly glued to 
   G5                 C5                   F5 
   this extraordinary mood.  So now move o- ver   let me take 
F#5 
over    with my 
F5   F#5      Ab5   Bb5    Eb5 
      Mel - an - chol - y      Blues 

Solo :  
Eb5  Bb5  B5   C5   Ab5   Ab5   Eb5   F#5   F5   F#5   E5    E5   F5  Fm^  F5  F5  
 
Ab5 
   I'm causing a mild sensation 
Ab5 
   With this new occupation 
Eb5          C5 
   I'm in the news 
   G5               C5              F5 
   I'm just getting used to my new exposure 
F#5 
   So come into my enclosure 
 
And meet my 
F5  F#5     Ab5   Bb5    Eb5 
    Mel - an - chol - y      Blues 
 
Album Ending : Song Fades out using the following Chords to the same style / melody of the piece. 
E5   B5   B5   C5   A5   A5   E5   F#5   F5   F#5   F5   F#5   A5   B5   E5 
Concert Ending : Song uses the Album Ending chords and resolves on E - obviously with no fade. 
  
Performance Notes :  

^ means the chord is played on 1 octave higher on the register. 

Ad-Libbing on the song can be achieved by trilling on neighboring notes on the scale / chord. 

Listening to the Album / Concert version will allow you to place a more-true ad-lib. 

The song also contains many 7th and diminished notes. 

The timing in the song is a little unusual in that its very free and chords are often played  

in advance of the words - best bet is to listen to the piece on the album a few times to get 

the idea.