The key of A minor uses mostly the notes of the A natural minor scale (A, B, C, D, E, F and G) and of the A harmonic minor scale (A, B, C, D, E, F and G#), and sometimes from the A melodic minor scale (A, B, C, D, E, F# and G#).
The key signature has neither sharps or flats, and its relative major key is C major which has the same key signature.
Famous songs in the key of A minor include Californication by the Red Hot Chili Peppers and Dream of Mirrors by Iron Maiden.
A Minor Diatonic Chords
Since the A minor key often combines two or more scales, it is used in a number of chords. Here are some examples:
Scale degree chords of the A natural minor scale:
i ii° III iv v VI VII
Am Bmb5 C Dm Em FG
Scale degree chords of the A harmonic minor scale:
i ii° III+ iv V VI VII°
Am Bmb5 C+ Dm E F G#mb5
Scale degree chords of the A melodic minor scale:
I ii III+ IV V vi° vii°
Am Bm C+ D E F#mb5 G#mb5
The most common chords in A minor are from the A natural minor scale, except for the 5th scale degree which is borrowed from A harmonic minor:
i ii° III iv V VI VII
Am Bmb5 C Dm E F G