Scales to Play Over A5

An A5 chord contains the notes A – E. Any scale that includes every one of those 2 tones fits over it — from the root A, that means A Major, A Natural Minor, A Melodic Minor, A Harmonic Minor, A Major Pentatonic, A Minor Pentatonic, A Blues, A Rock 'n' Roll, A Dorian, A Phrygian, A Lydian, A Mixolydian, A Dorian Bebop, A Mixolydian Bebop, A Half Whole Diminished, A Spanish, A Gypsy Major and A Gypsy Minor. They differ only in the notes between the chord tones, and that is where each scale gets its color.

A5 is also diatonic to 6 major keys: A major (relative minor F#m), C major (relative minor Am), D major (relative minor Bm), E major (relative minor C#m), F major (relative minor Dm), G major (relative minor Em). In a song from one of those keys you can also solo with the key's own major scale or its relative minor pentatonic across the whole progression, not just this chord.