u/mercimer

I'm transcribing the chords to Some Velvet Morning by Nancy Sinatra and Lee Hazlewood and there is an orchestral intro playing what sounds like Ab - gm - G - f#m leading to the verse in f#m. It seems like twice you have a similar resolution going from a major chord down to the minor chord a half step below, can anyone point me in the way of any theory describing this? Also the change from gm - G is lovely in the way it keeps the progression moving.

Does anyone recognize this sequence from somewhere else? I feel the melody ought to give some clues to whats going on as well...