In this video
Theory point - why Bb and not A#?
The A-sharp key is rarely used in practice because it is too complex to use. In A-sharp, every note is a sharp and degrees 3, 6 and 7 are double-sharped (written G##). It is not on the Circle of fifths diagram, which contains the most commonly used keys.
There is an identical major scale of Bb, which is on the Circle of 5ths and this tends to be used in its place.
Chords in the key of Bb major; Bb major, C minor, D minor, Eb major, F major, G minor, A diminished.
So yes, the notes are the same. But writing them in Bb rather than A# prevent nasty double sharps that are harder to understand when reading music or chord charts.
Phew! Now that's over, see below the interactive tab for this 12 bar blues boogie woogie in Bb!
Interactive tab
Course Outline
Acoustic Looper Bootcamp