I use B 7 a lot as a sub for Ebo 7 which BTW I prefer spelling as D # o 7 . As far as the rest of it , I ' ve found wholehalf diminished scales easy to learn and teach , but not so easy to put into practice . In general I don ' t like rules , but one which may help in this situation is if you ' re starting a line using a diminished scale in 8 th notes the note on the downbeat should be a whole step away from the the note on the upbeat , going up or down . The next rule is to resolve to a tone in the next chord that ' s close to your last note in the diminished scale . I ' ll use an example if you had a measure of each chord Em 7 D # o 7 Dm 7 G 7 , and I ' m just going to focus on the D # o 7 to Dm 7 . Playing 8 th notes I have 8 notes over the D # o 7 , so if I play D # E # F # G # A B C D the full 8 note scale going up I can resolve up to an E , the 9 th of the Dm 7 . I could also play the scale up and go down to the C , the 7 th of the Dm 7 . When you ' re going up the scale that means you ' re starting on one of the chord tones of the diminished chord . If , however , you start with a nonchord tone on the downbeat the answer is simple you just go down the scale . Let ' s say I end up starting on the note B on the D # o 7 . If I go down the scale in 8 ths it ' s B A G # F # F D # D C , so I can go back up to D for the Dm 7 , or if I hit the B I can use it as an approach tone to the C in the Dm 7 . These same techniques work going from the IV chord to the # IV diminished in fact they work anytime you ' re using wholehalf diminished scale over a diminished chord , and they also work the same way when you ' re using them over 7 b 9 chords , you just have to remember that the root of the dominant chord is a 12 step below the next scale tone . It ' s easier , then , if you ' re going up the scale over a dominant chord to start it on a downbeat over the 3 rd , 5 th , or b 7 th of the chord . Once you ' re practiced the diminished scale this way you can loosen to rules up and be more spontaneous . If , for example , you get off on the wrong foot going up or down you can skip a note in the scale to get back on track . Now that I ' ve said all that , in reality there are no avoid notes in diminished scales they all can function as chord tones but I ' ve noticed that they do have certain tendencies towards resolving , and to it ' s made the difference between smooth and awkward sounding phrases . Hope this helps .