I think it's in the key of C minor. Or, actually maybe it's C Dorian? Who cares. :D
The main part is:
The Blues for Mama bit is: [Cm][Cm][Gm][Gm] x2
The rest her soul bit is:
[Eb][Eb][F][F]
[Gm][Gm][Eb][F]
The modulated bridge part at the latter part of the song, starts at around 1m35s, is:
[Bb][Bb][Ab][Ab]
[Bb][Bb][Ab][Gm]
acoustic solo bit 1m54 - 2m07s:
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-12'-10-8-10 12'-12'-10-8-10~-10H12-8-(10)------------
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-10-12'-10-8-10H12s...-----------------------8~-(10)--
-----------------------2S13H15-8~-8-10-8--10----------
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The solo after 3min kicks in the same C minor pentatonic kicks off
...approximately like this:
-----------------------------------------------------
-11^~-11-13----13-11---------------------------------
-----------12-----------10-12-10-10-8----------------
--------------------------------------10-8-10-8------
--------------------------------------------------10-
-----------------------------------------------------
