Yeah, it's in the key of D minor.

The chord progression includes an A dominant 7 which allows you to resolve to the key center. ( Dm )

Because of the Dominant chord, the scale that best fits is the Harmonic minor.

But in Music Theory there is no " Harmonic minor key "...instead you place a minor key signature and the raised seventh appears as an accidental.

The F major scale that you were using has a natural C note, whereas the D Harmonic minor has a C#.

Most of the notes of the scale you were playing fit, just make sure to play the C# over the A7 chord.


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