I am analysing an arrangement of "Over the RainBow", arranged by Walter Rodriguez:
Looking at his musical score (not at what he is actually playing), the first chord he offers is just a straight C. Ok, he is in C major. Here is the mystery: the second chord in bar 2 is played for 2 beats. It is an Fm7(b5) which is made up of F Ab Cb Eb. My question is, how is it that when playing in C major, you have got notes which do not appear in the key of C major? Specifically,the Ab is a flat 6th in C major, the Cb is a lowered tonic, the Eb is a minor 3rd. And yet it sounds fine. What is going on? Can someone explain this to me? It makes my head explode. Thanks !