Bb Phrygian

The Bb Phrygian mode (also written A#) — Bb Cb Db Eb F Gb Ab — shown across the guitar neck.

Also written A# Phrygian. A# and Bb are the same pitch — Bb is the spelling in common use.

Swipe the neck sideways to see the higher frets.

Bb Phrygian is the natural minor with one note changed — the b2, Cb. That single note is what the mode sounds like; lean on it and the colour is obvious, avoid it and you are just playing minor.

The tool shows this from its parent key, F# major, with A# — the same pitch as Bb — marked as where Phrygian begins, the same seven notes centered on F#.