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Would anybody know the parent major scale of F sharp minor 7 flat 5?

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G major. F#, A, C, E make F#m7b5, the 4 note chord based on the leading note of G major. The triad would be F#o, and your chord is sometimes called F# half-diminished. There's a sign, but I can't find it!

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  • The diminished chord is a superscripted little circle like you approximated with an 'o'. The half-diminished chord is the same but with line through it like this ø. Is that what you meant? Or you just couldn't find how to type the character? Either way...
    – user37496
    Apr 26 '17 at 12:52
  • I haven't got to where I am without knowing..! The approximation is actually dim - F#o. But I don't know how to make half-dim with a qwerty board.
    – Tim
    Apr 26 '17 at 14:06
  • Press/hold the "alt" key and type 232 on the 10-key num pad to get this symbol: Φ Hope this helps! Sep 13 '17 at 22:19
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    ø - It's here: en.wikipedia.org/wiki/Half-diminished_seventh_chord You can just cut and paste it from here or any place you find it on interweb - put one aside if you like.
    – Stinkfoot
    Sep 14 '17 at 3:43
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    @Greg - yes, either will work, 'cos every other note from them is contained within the chord - assuming you pick the right one from three! However, m7b5 is not a dim chord - it's only sort of half dim. The m7 bit is what makes the difference: dims have a dim7, a semitone lower than the b7 (m7).
    – Tim
    Sep 14 '17 at 14:37
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There are two likely choices for the parent scale of an F♯-7(♭5) chord, also known as an F♯∅ or half-diminished chord.

This chord can be built on the seventh degree (or the Locrian mode) of the major scale, meaning that G major could be thought of as the parent scale for this chord. From F♯ Locrian this gives:

    F♯  A   C   E   G   B   D  
    1  ♭3  ♭5  ♭7  ♭9   11 ♭13

But you can also build this chord on the sixth degree (or the Locrian #2 mode, or the half-diminished mode) of the melodic minor scale. This would make the A melodic minor scale a parent scale of the half-diminished chord. From F♯ Locrian #2 this gives:

    F♯  A   C   E   G♯  B   D  
    1  ♭3  ♭5  ♭7   9   11 ♭13

Note that the only difference between these two approaches is in the 9th. The Locrian mode from the major scale provides a lowered 9th; this is sometimes called an "avoid" note since it is a half-step above a chord tone and is harmonically unstable. The Locrian #2 mode from the melodic minor scale provides a natural 9th. None of the upper extensions are a half-step above a chord tone, so there are no "avoid" notes here.

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    Two more for completeness: 2nd mode of harmonic minor (locrian ♮6), and half-whole tone. Jan 14 at 15:50
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The most common usage of half-diminished chords (min7b5) is as the ii chord in a minor key. In that regard, the parent scale of F#min7b5 is E minor, which, of course, is the relative minor to G major, where F#min7b5 is the vii chord.

A characteristic use of the half-diminished chord is within a ii-V-i chord progression. Here's a classic example: the beginning of the bridge in "Autumn Leaves":

"Autumn Leaves" bridge excerpt

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  • and often you would want to be thinking of the harmonic minor, for exactly that reason
    – Judy N.
    Jan 14 at 15:20
  • @MichaelCurtis - decent - descent is definitely going downhill...
    – Tim
    Jan 14 at 20:26
  • Up voted this, down voted the others. How could any decent answer not first mention the basic iim7b5 V i progression as the commonest use in jazz. Used a lot in Impressionism, but I don't think that's the OP's context. Jan 14 at 20:27
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In G Major (Ionian mode) the F♯ is the 7th scale degree. It is best to keep it simple, you could analyze it forever. I suggest grabbing your instrument and practice. Make music, regardless of what scales are available and where it is derived from, play, have fun and don't over think it. Enjoy and you can find a parent scale from one chord. Absolutely.

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    This isn't answering the question asked. It may get downvoted because of that fact.
    – Tim
    Apr 21 '20 at 7:56
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One cannot find the parent scale from just a chord. Maybe it could be a G major, but this chord could be also a Dominant of Dominant (D.D) VII7, which leads to G major, which is the V of C scale

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    Given a major triad, there would be three diatonic possibilities: e.g. (D F# A) is in the keys of G, D, and A. The same could be said for minor triads. But a m7b5 chord narrows down the diatonic possibilities to one. Jan 25 '18 at 20:09

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