Guide Tones I

The Guide Tones I voicing of C#7b9 stacks E# and B from the bottom up: the major 3rd and minor 7th of the chord. It leaves out the root, C#, for the left hand or the bass player to take.

It's one of the Guide Tones voicings: just the 3rd and 7th, the notes that define each chord, played over the root. The other for C#7b9 is Guide Tones II.