I'm always been interested in what actually constitutes an arrangement. Take for example The Animals arrangement of The House of the Rising Sun. Now, as we all know, The Animals got this song from Bob Dylan's first album. They kept Dylan's chord progression ( which he, in turn, got from Dave Van Ronk)and added an arpeggiated guitar backing and sustained organ chords ( and drums and bass, of course). Now, this song is copywrited as arranged by the organist Alan Price ( much to the chagrin of the rest of the band). Now, the part of The Animals' arrangement that was most distinctive, and certainly the feature that was picked up on by most bands at the time, was the arpeggiated guitar chords. I wonder if that was the guitarists idea, or did Alan Price suggest that to him?