A natural minor scale with raised fourth

Question

Good day

I am trying to understand what scale/mode is created by raising the fourth of a natural minor. It sounds quite dark. I understand that natural minor is the Aeolian mode of the major scales, thus, natural minor cannot have its own sets of modes, is this right?

Regardless, the piece of music center on the tonic, in this case A minor in the left hand on the piano with many diatonic chords of A minor in the right hand, all of which has no sharp or flats, thus pure A natural minor. So tonal center is kept in A and in a minor scale throughout, but then there is a F dominant 7th chord that resolves back to Am. Surely this must be a modal change? The F7 chord is F A C D#. The Mixolydian scale of F has a Bb and Eb. The piece I am playing has no B flats. I don't believe the gypsy scale nor double harmonic scale explained this case.

By all means, correct me if I'm wrong. Thank you in advance for any explanations.

Answer 1

If you have a natural minor with a raised fourth (#4), let's say starting from A, you would have A B C D# E F G (A) . If you start that scale from E, you would get the minor Neapolitan scale, in which scale the fourth mode is Natural Minor ♯4 or Romani Minor or Aeolian #4.

This mode has the scale degrees you were asking about:

The F7 chord is F A C D#. The Mixolydian scale of F has a Bb and Eb.

You have a mistake here. The F7 chord would be F A C Eb (Eb, not D#). Without the song you are referring to, it's hard to be sure what the F7 chord is there for.

Answer 2

I would not be too concerned by notes not in the scale, all notes can be used without weakening the tonality. For instance, think of the numerous hymn tunes that use chromatic chords. In the key of C the harmonic progression of C D7 G is an imperfect cadence that does not affect the sense of tonality.

In traditional harmony the chord of F A C D# is perfectly acceptable and does not imply a change of mode. It is an effective cadential chord because the D# resolves upwards to E and the F resolves down to E. The difference is that in traditional classical harmony, this chord would usually be followed by the dominant chord on E - with or without the 7th. The dominant chord E could be preceded by the 2nd inversion of Am but probably never Am in root position.

The chord you describe is not a dominant seventh chord - as Shevliaskovic pointed out - as it is D# not Eb. It's an augmented sixth chord, a German sixth to be precise. You can find more information here:

Augmented 6th chords

Answer 3

If the resolving chord is Am/E (slash chord am64) and not Am in root position this is 100% a German6th.