Based on my knowledge, here are the diatonic seventh chords in A minor:
In natural minor:
- Am7, Bm7♭5, Cmaj7, Dm7, Em7, Fmaj7, G7
In harmonic minor:
- Am(maj7), Bm7♭5, Caug(maj7), Dm7, E7, Fmaj7, G♯dim7
In melodic minor:
- Am(maj7), Bm7, Caug(maj7), D7, E7, F♯m7♭5, G♯m7♭5
However, I got this comment on one of my posts:
C Major/ A minor are diatonic and do not have any accidentals. If you are suggesting chord with accidental they are not diatonic. For example, while E7 is use in classical composition all the time it is not a diatonic chord of A minor.
Is E7 really non-diatonic to A minor?