B♭ 9♭5 Chord
B♭ 9♭5 is built from the notes B♭, C, D, E, A♭. The interval from B♭ to C is a major 2nd (2 semitones), from B♭ to D is a major 3rd (4 semitones), from B♭ to E is a tritone (6 semitones), from B♭ to A♭ is a minor 7th (10 semitones). This chord contains 2 flatted notes.
The 7♭9♯9 stacks both altered ninths on a dominant chord, creating maximum chromatic tension. It's a rare, aggressive altered sound used when you want the most dissonant dominant possible before resolving.
Built from R, 3, ♭7, ♭9, ♯9 (the 5th is typically omitted), this chord piles two clashing altered tones on a dominant 7th. The ♭9 and ♯9 sit only a whole step apart, creating intense friction. It functions as a supercharged dominant chord that can resolve to either major or minor.
This voicing is extremely tight on guitar — you need to carefully select which notes to include. A practical approach is to voice it with root, 3rd, ♭7, and either the ♭9 or ♯9 on adjacent strings, implying the other. Most guitarists encounter this sound through the altered scale rather than a specific grip.