B natural with a B flat scale?
In the bluesy scale I wrote in the previous post there is no B natural, although there is a A natural which sounds good especially when resolving to Bb in the last bar.
A B natural would be the second note of Balt scale, which is an option on the Bb7 chord in the first bars of a Bb blues (or in 5th and 6th bars of a F blues)
Bb-B-Db-D-E-Gb-Ab-Bb
In strict theoretical terms, the above would be a B natural melodic minor scale
Mark Levine's Jazz theory book explains it very clearly. Melodic minor scale harmony in Bb is played on the following chords:
Bnatural minor-major (min 7+)
Db sus b9
Dmaj#5
E7#11
B minor-major/G
Ab half diminuished
Bb7 alt
I'm not so good to remember all them, I'm reading from Levine's book.
