Four sharps, and not one of them lands on A. That single detail is what G# Phrygian is all about. Its notes are G#, A, B, C#, D#, E, F#, and that plain, unsharpened A sitting just above the root gives this mode its shadowy, slightly menacing color. The quickest way to understand it is to start from a scale you may already know and change exactly one note.
G# natural minor, the ordinary minor scale in this key, runs G#, A#, B, C#, D#, E, F#. It's a sad, settled sound, and its key signature has five sharps. A key signature is simply the list of sharps or flats written at the start of a piece so you don't have to mark them on every note.
Now take the second note, A#, and lower it by a half step to A. A half step is the smallest step in Western music, like moving from one piano key to the very next one, black or white. That one change turns G# minor into G# Phrygian. Everything else stays put.
In the shorthand musicians use, this lowered note is called the flat 2nd, written b2. The full formula reads 1, b2, b3, 4, 5, b6, b7. Each number describes how far a note sits from the root, the home note, which here is G#. The b3, b6 and b7 are shared with ordinary minor. The b2 is the newcomer, and it's the one you'll hear.
Every seven-note scale like this uses each letter name once: G, A, B, C, D, E, F. That rule keeps the music easy to read. So the note after G# has to be some kind of A, and since we want it a half step above G#, it's plain A. The rest follow the same logic, giving G#, A, B, C#, D#, E, F#.
You might also see this mode written as Ab Phrygian. It sounds identical, but on paper it needs the equivalent of 8 flats, which means some notes would carry double flats. Nobody enjoys reading that. G# is the friendlier spelling, and if the Ab version ever shows up, don't worry: same sound, just heavier paperwork.
Here's a handy trick. Those seven notes are exactly the notes of E major: E, F#, G#, A, B, C#, D#. E major is called the parent scale, and it carries four sharps: F#, G#, C# and D#. G# Phrygian uses the same four-sharp signature. The difference is purely where you treat as home. Play those notes and keep landing on E, and you hear bright major. Keep landing on G#, and the very same notes turn dark.
On piano, try this: play E major from E to E, then play the same white and black keys from G# up to G#. Your fingers barely change, yet the mood flips.
A whole step is two half steps, like skipping one key on the piano. Phrygian follows the pattern H - W - W - W - H - W - W. Walk it from G#:
That half step right at the start is the fingerprint. Most scales begin with a whole step; Phrygian crowds the root immediately.
Stack every other note of the scale and you get its chords. Roman numerals show which scale step each chord starts on, with lowercase for minor:
The chord that sells the sound is A major, the bII. Moving between G#m and A, a half step apart, is the classic Phrygian gesture you hear in flamenco and heavy metal. Try G#m – A – B – A – G#m, slowly, letting the A chord lean back down onto G#m each time. Avoid leaning on E major too long, or your ear may start hearing E as home.
Melodies in G# Phrygian love to hover around the root and dip up to A, then fall back. Sing G#, A, G# and you'll feel a sigh, almost a groan. That tiny rub is why the mode reads as tense and exotic. Phrases that end by stepping down from A to G# sound especially final and dramatic.
Songwriters and producers often keep the bass droning on G# while the melody circles A, B and C#. Horn and string players can get a lot of mileage from slow, swelling A-to-G# resolutions.
Your root sits on the low E string at frets 4 and 16, and on the A string at frets 11 and 23. Anchor on fret 4, play the open-sounding G# there, and try the half-step move to A at fret 5. Then drop to the A string's 11th fret for a second root and repeat the same rub an octave up.
Hold a low G# (piano, bass, or just hum it), and sing or play only three notes over it: G#, A, B. Make up a four-bar phrase that ends A to G#. Then change that A to A# and sing it again. Hearing the mood drain out tells you exactly what the b2 was doing.
For the bigger picture, read The Phrygian Mode.