Type B

The Type B voicing of Ab7alt stacks Gb, B, C and E from the bottom up: the minor 7th, sharp 9th, major 3rd and sharp 5th of the chord. It leaves out the root, Ab, for the left hand or the bass player to take.

It's one of the 4-Note Rootless (Type A/B) voicings: four-note rootless voicings in their two forms, with the 3rd or the 7th on the bottom, played over the root. The other for Ab7alt is Type A.