Half-Whole Diminished (lesson)
The Half-Whole diminished scale is one of a larger class of 8 tone scales known generically as BeBop scales. It is actually a mode of the Diminished scale, and owing to its construction and the fact that it has 8 tones, it actually repeats its pattern every 2 steps, meaning that it can serve as multiple modes for the parent scale. In this case it is modes II, IV, VI and VIII, whilst the parent scale (The Whole-Half diminished) serves as the other modes.
This scale is used a lot in Jazz, and plays well over a range of diminished chords. The Half-whole scale is commonly used over a Dominant chord too, and while this seems like a strange choice (m7b5 chords should suit it better) it yields some altered tones that jazzers like.
Number of tones : 8
Intervals : 1,b2,b3,3,#4,5,6,b7
Formula : 1,2,1,2,1,2,1,2
Characteristic Chords : Half Diminished, Diminished, Minor 7, Diminished 7