I thought it best to start with one which, while being one of the most beloved films of all time, is rarely mentioned in best soundtracks lists. It is To Kill a Mockingbird.
The score was composed by Elmer Bernstein, who also did The Great Escape, The Magnificent Seven and Ghostbusters (and many others). The main theme, played over the opening credits of the film, is a perfect example of what makes a great film score: it captures the themes and ideas of the film and presents them to you before any line of dialogue is uttered. Nostalgic images of childhood are conjured, an innocence is evoked in the simple piano theme, which is then given full body by the solo flute and then orchestra. The simple piano motif comes back after the cresendo, a contemplative counter-point to the blossoming of sound we have just heard.
The film's themes of innocence, both of children and in the criminal justice system, are beautifully realised in this piece. The more minor chords that come after the swell of sound imply the hard lessons Jem and Scout are to learn, the pain of growing up and discovering the world is not as good as it should be. While it is one of the least talked about elements of Robert Mulligan's adaptation, with most praise being given to the script and the performances, Bernstein's soundtrack draws us into this world of 1930s Alabama and the joys and pains of childhood.