Although Glass writes for a number of different genres such as chamber instruments and operas, his film music is perhaps what he is most famous for. He started writing for film in 1982 for the film 'Koyaanisqatsi' however his most famous scores are for 'The Truman Show' (1998) - of which he only composed part of the score, 'The Hours' (2002) and 'Notes on a Scandal' (2006). Notice how each of these films have deep psychological turmoil within the characters - something which Glass' music represents perfectly. 'The Truman Show' is a particularly good example of the incredible skill Glass has for piano writing. The famous cue, 'Truman Sleeps' is very effective, as the solo piano creates circles of hypnotic harmonies to mimic Truman as he sleeps, and reflects the underlying tragedy of the film.
In my opinion, his best score is for 'The Hours'. As a film that follows the lives of three women who all suffer from psychological confusion and pain, there couldn't have been a better person to compose the score. One cue in particular which captures the essence of the entire score is the introductory passage titled, 'Morning Passages'. This is heard as we watch each of the three main characters wake up and start their day. When analysing the score, there is an incredible amount of detail which - because of it's subtlety - is typical of Glass when trying to recreate human emotions in music. First of all, this cue is definitely not minimalistic as the phrases - or cells - are constantly changing, whereas if we look at previous works of Glass such as his opera 'Satyagraha', there are scenes in which the music would stay the same for about ten or fifteen minutes at a time.
Similarly to 'Truman Sleeps' the cue is written mainly for solo piano, with the addition of strings for a deeper tone. For most of the cue, Glass plays with the same cell, and changes it usually about every or every other bar. His harmony is not that of more classical modulations, but instead he tends to create more lyrical and chromatic harmonies. This is accompanied by an extremely chromatic piano right hand as well. As the music starts, in the third and sixth bar, the music pauses to reflect the contemplative nature of the women that we are watching on the screen. As well as this, the strings enter in octaves on long, held chromatic notes. Despite the fact most critics refer to Glass' music as 'classical', we can actually see a lot of classical influences in the score that date back even to J.S.Bach. His influences of Bach can be heard in his unexpected and intricate use of harmony. We can even see influences of Beethoven in his piano triplets, and Mozart with his occasional use of rotary octaves in the right hand. Glass even adds in clever touches such as a trill in the piano as the women's alarm clocks go off. For the most part, the tonality of the cue is minor, and, although it may seem extremely ominous compared to what is going on on-screen, (e.g. three women brushing their hair and washing their faces in the mirror) this shows how Glass' scores are wonderful at pointing out the underlying problems of the characters.
Despite the fact the rest of the score has little variation, I think it is extremely effective because despite the fact that Glass rarely uses melodies and instead creates suspense in his harmonies, this creates more of an atmosphere in the film. After all, a good film score should not be noticeable and not intrusive.