A#7b5 chord
A# dominant seventh flat five
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3
5
7
10
The A#7b5 chord has the formula 1, 3, b5, b7 with notes A#, D, E, G#
The seventh flat five chord is a variation of the dominant seventh chord. It is sometimes used as a passing chord in jazz tunes to resolve at a major or minor seventh chord one half-step down.