This jam focuses on what to be aware of when playing in a minor key, which is more than simply knowing the relative major key.
Theory points
A minor is the relative minor key to C major. Both keys have no sharps or flats and broadly speaking all the same diatonic chords. However, as there are 3 minor scale options, it gets a bit more complicated, but all you need to know is that the minor iii chord in the major key (E minor chord in the key of C major) is often made major so to match both the harmonic minor and melodic minor scales.
Chords in the key of C major are; C major, D minor, E minor, F major, G major, A minor (and the rarely used B diminished chord)
The same chords occur in the key of A minor starting from the A minor and going in the same order. However, the E chord is made made to match the G# note found in both the harmonic minor and melodic minor scales.
Chords in the key of A minor are typically; A minor, B diminished, C major, D minor, E major, F major and G major.
Regardless of whether you know minor scales or not, the only thing you need to remember is;
In the key of A minor - E major is often used in place of E minor.
That's it! :) The same is done to the same diatonic chord in any minor key also.
Scales to know - A natural minor scale
Exactly the same notes as the C major scale, but the A note becomes the root.
A harmonic minor scale
Same notes but with the G sharpened to G# to match the harmony of the E major chord (which has a G#)
A melodic minor scale
Same notes as above but with the F sharpened to F#, which in practice should give a more pleasant melody, hence the name melodic minor
Full example - Interactive tab
See below some recommended song tutorials as further examples of chord progressions and melodies in the key of A minor.
Recommended song 1 - House Of The Rising Sun by The Animals
Classic example where we have all the same chords as the key of C major, but with E major rather than E minor.