The 12 Bar Blues in Bb contains the chords Bb7 (I chord), Eb7 (IV chord) and F7 (V) chord. Below is the 12 Bar Blues starting on Bb7.
12 Bar Blues in Bb (Jazz Variation)
The Jazz variation of the 12 Bar Blues in Bb adds some extra chords. The 12 Bar Blues structure remains the same, but certain chords are substituted. For example, the Bb7 chord in the fourth bar is substituted with an Fm7 moving to an Ab7 chord.